<PAGE>   1
   As filed with the Securities and Exchange Commission on September 26, 2000


                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                    FORM S-8
                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933

                             ----------------------

                             KLA-TENCOR CORPORATION
             (Exact name of registrant as specified in its charter)

          Delaware                                     04-2564110
  (State or other jurisdiction             (I.R.S. Employer Identification No.)
of incorporation or organization)


                   160 Rio Robles, San Jose, California 95134
               (Address of principal executive offices) (Zip Code)

                             KLA-TENCOR 401(k) PLAN
                            (Full title of the plan)

                                Stuart J. Nichols
                       Vice President and General Counsel
                             KLA-Tencor Corporation
                   160 Rio Robles, San Jose, California 95134
                     (Name and address of agent for service)

   Telephone number, including area code, of agent for service: (408) 875-3000

                                   Copies to:

                             Larry W. Sonsini, Esq.
                          Christine L. Richardson, Esq.
                      Wilson Sonsini Goodrich & Rosati, PC
                               650 Page Mill Road
                           Palo Alto, California 94304

<TABLE>
                                  CALCULATION OF REGISTRATION FEE
============================================================================================================
                                             Proposed Maximum       Proposed Maximum
Title of Securities to      Amount to be    Offering Price Per     Aggregate Offering       Amount of
    be Registered            Registered           Share*                 Price*         Registration Fee*
------------------------------------------------------------------------------------------------------------
<S>                        <C>              <C>                    <C>                  <C>
Common Stock, $0.001 par   500,000 shares        $43.50                $21,750,000            $5,742
value**
============================================================================================================
</TABLE>

*        Estimated solely for the purpose of calculating the registration fee
         pursuant to Rule 457(c) under the Securities Act of 1933, on the basis
         of $43.50 per share, the average of the high and low prices per share
         of the Common Stock on the NASDAQ National Market on September 22,
         2000.

**       Associated with the Common Stock are Common Stock Purchase Rights that
         will not be exercisable until the occurrence of certain prescribed
         events, none of which has occurred. In addition, pursuant to Rule
         416(c) under the Securities Act of 1933, this registration statement
         also covers an indeterminate amount of interests to be offered or sold
         pursuant to the KLA-Tencor 401(k) Plan described herein.



<PAGE>   2
               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

ITEM 3. INCORPORATION OF DOCUMENTS BY REFERENCE

The following documents are incorporated by reference in this registration
statement: (i) the latest annual report of KLA-Tencor Corporation (the
"Registrant") filed pursuant to Section 13(a) or 15(d) of the Securities
Exchange Act of 1934, as amended (the "Exchange Act"); (ii) all other reports
filed by the Registrant pursuant to Section 13(a) or 15(d) of the Exchange Act
since the end of the fiscal year covered by the annual report referred to in
clause (i) above; and (iii) the description of the Registrant's common stock set
forth in the Registrant's Registration Statement on Form 8-A relating thereto,
including any amendment or report filed for the purpose of updating such
description. All documents filed by the Registrant or the KLA-Tencor 401(k)
Plan, as amended, after the date of this registration statement pursuant to
Sections 13(a), 13(c), 14, and 15(d) of the Exchange Act, prior to the filing of
a post-effective amendment (that indicates all securities offered have been sold
or deregisters all securities then remaining unsold), shall be deemed to be
incorporated by reference in this registration statement and to be a part hereof
from the date of filing of such documents.

ITEM 4. DESCRIPTION OF SECURITIES

Inapplicable.

ITEM 5. INTERESTS OF NAMED EXPERTS AND COUNSEL

Inapplicable.

ITEM 6. INDEMNIFICATION OF DIRECTORS AND OFFICERS

Section 145(a) of the Delaware General Corporation Law (the "DGCL") provides in
relevant part that "[a] corporation may indemnify any person who was or is a
party or is threatened to be made a party to any threatened, pending or
completed action, suit or proceeding, whether civil, criminal, administrative or
investigative (other than an action by or in the right of the corporation) by
reason of the fact that he is or was a director, officer, employee or agent of
the corporation, or is or was serving at the request of the corporation as a
director, officer, employee or agent of another corporation, partnership, joint
venture, trust or other enterprise, against expenses (including attorneys'
fees), judgments, fines and amounts paid in settlement actually and reasonably
incurred by him in connection with such action, suit or proceeding if he acted
in good faith and in a manner he reasonably believed to be in or not opposed to
the best interests of the corporation, and, with respect to any criminal action
or proceeding, had no reasonable cause to believe his conduct was unlawful."
With respect to derivative actions, Section 145(b) of the DGCL provides in
relevant part that "[a] corporation may indemnify any person who was or is a
party or is threatened to be made a party to any threatened, pending or
completed action or suit by or in the right of the corporation to procure a
judgment in its favor... [by reason of his service in one of the capacities
specified in the preceding sentence] against expenses (including attorneys'
fees) actually and reasonably incurred by him in connection with the defense or
settlement of such action or suit if he acted in good faith and in a manner he
reasonably believed to be in or not opposed to the best interests of the
corporation and except that no indemnification shall be made in respect of any
claim, issue or matter as to which such person shall have been



                                       2
<PAGE>   3
adjudged to be liable to the corporation unless and only to the extent that the
Court of Chancery or the court in which such action or suit was brought shall
determine upon application that, despite the adjudication of liability but in
view of all the circumstances of the case, such person is fairly and reasonably
entitled to indemnity for such expenses which the Court of Chancery or such
other court shall deem proper."

The Registrant's Amended and Restated Certificate of Incorporation provides that
to the fullest extent permitted by the DGCL, no director of the Registrant shall
be personally liable to the Registrant or its stockholders for monetary damages
for breach of fiduciary duty as a director. The Amended and Restated Certificate
of Incorporation also provides that no amendment or repeal of such provision
shall apply to or have any effect on the right to indemnification permitted
thereunder with respect to claims arising from acts or omissions occurring in
whole or in part before the effective date of such amendment or repeal whether
asserted before or after such amendment or repeal.

The Registrant's Bylaws provide that the Registrant shall indemnify to the
fullest extent permitted by the DGCL each of its directors, officers, employees
and other agents against expenses actually and reasonably incurred in connection
with any proceeding arising by reason of the fact that such person is or was an
agent of the Registrant.

The Registrant has entered into indemnification agreements with its directors
and executive officers and intends to enter into indemnification agreements with
any new directors and executive officers in the future.

ITEM 7. EXEMPTION FROM REGISTRATION CLAIMED

Inapplicable.

ITEM 8. EXHIBITS

4.1      KLA-Tencor 401(k) Plan (July 1, 1997 Restatement), as amended by
         Amendments No. 1 through 4 thereto.

5.1      Undertaking re Status of Favorable Determination Letter Covering the
         Plan.

         The Registrant has received a favorable determination letter from the
         Internal Revenue Service (the "IRS") concerning the qualification of
         the KLA-Tencor 401(k) Plan (the "Plan") under Section 401(a) and
         related provisions of the Internal Revenue Code of 1986, as amended.
         The Registrant will submit any future material amendments to the Plan
         to the IRS with a request for a favorable determination that the Plan,
         as amended, continues to so qualify.

23.1     Consent of PricewaterhouseCoopers LLP.

24.1     Power of Attorney of Directors.



                                       3
<PAGE>   4
ITEM 9. UNDERTAKINGS

         (a) The undersigned Registrant hereby undertakes:

                  (1) To file, during any period in which offers or sales are
being made, a post-effective amendment to this registration statement:

                           (i) To include any prospectus required by section
10(a)(3) of the Securities Act of 1933, as amended (the "Securities Act");

                           (ii) To reflect in the prospectus any facts or events
arising after the effective date of the registration statement (or the most
recent post-effective amendment thereof) which, individually or in the
aggregate, represent a fundamental change in the information set forth in the
registration statement;

                           (iii) To include any material information with
respect to the plan of distribution not previously disclosed in the registration
statement or any material change to such information in the registration
statement;

Provided, however, that paragraphs (a)(1)(i) and (a)(1)(ii) do not apply if the
information required to be included in a post-effective amendment by those
paragraphs is contained in periodic reports filed by the Registrant pursuant to
Section 13 or Section 15(d) of the Securities Exchange Act of 1934, as amended
(the "Exchange Act") that are incorporated by reference in the registration
statement.

                  (2) That, for the purpose of determining any liability under
the Securities Act each such post-effective amendment shall be deemed to be a
new registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof.

                  (3) To remove from registration by means of a post-effective
amendment any of the securities being registered which remain unsold at the
termination of the offering.

         (b) The undersigned Registrant hereby undertakes that, for purposes of
determining any liability under the Securities Act, each filing of the
Registrant's annual report pursuant to Section 13(a) or Section 15(d) of the
Exchange Act (and, where applicable, each filing of an employee benefit plan's
annual report pursuant to Section 15(d) of the Exchange Act) that is
incorporated by reference in the registration statement shall be deemed to be a
new registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof.

         (c) Insofar as indemnification for liabilities arising under the
Securities Act may be permitted to directors, officers and controlling persons
of the Registrant pursuant to the foregoing provisions, or otherwise, the
Registrant has been advised that in the opinion of the Securities and Exchange
Commission such indemnification is against public policy as expressed in the Act
and is, therefore, unenforceable. In the event that a claim for indemnification
against such liabilities (other than the payment by the Registrant of expenses
incurred or paid by a director, officer or controlling person of the Registrant
in the successful defense of any action, suit or proceeding) is asserted by such
director, officer or controlling person in connection with the securities being
registered, the Registrant will, unless in the opinion of its counsel the matter
has been settled by controlling precedent, submit to a court of appropriate
jurisdiction the



                                       4
<PAGE>   5
question whether such indemnification by it is against public policy as
expressed in the Securities Act and will be governed by the final adjudication
of such issue.



                                       5
<PAGE>   6
                                   Signatures

THE REGISTRANT


Pursuant to the requirements of the Securities Act of 1933, the Registrant
certifies that it has reasonable grounds to believe that it meets all of the
requirements for filing on Form S-8 and has duly caused this registration
statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the City of San Jose, State of California on the 25th day of
September, 2000.

KLA-TENCOR CORPORATION
(Registrant)

By /s/ Kenneth L. Schroeder
  ---------------------------
       Kenneth L. Schroeder
          President and
      Chief Executive Officer



Pursuant to the requirements of the Securities Act of 1933, this registration
statement has been signed by the following persons in the capacities and on the
dates indicated.

<TABLE>
<CAPTION>
        Signature                            Title                            Date
<S>                                    <C>                             <C>
Principal Executive Officer:


   /s/ Kenneth L. Schroeder            President and Chief             September 25, 2000
-----------------------------          Executive Officer
       Kenneth L. Schroeder



Principal Financial and
  Accounting Officer:


   /s/ John Kispert                    Executive Vice President        September 25, 2000
-----------------------------          and Chief Financial Officer
       John Kispert
</TABLE>



                                       6
<PAGE>   7
<TABLE>
Directors:
<S>                                    <C>                             <C>
              *                        Chairman of the Board           September 25, 2000
-----------------------------              and Director
         Kenneth Levy

              *                              Director                  September 25, 2000
-----------------------------
    Kenneth L. Schroeder

              *                              Director                  September 25, 2000
-----------------------------
     Edward W. Barnholt

              *                              Director                  September 25, 2000
-----------------------------
    Richard J. Elkus, Jr.

              *                              Director                  September 25, 2000
-----------------------------
       Dean O. Morton

              *                              Director                  September 25, 2000
-----------------------------
       Jon D. Tompkins

              *                              Director                  September 25, 2000
-----------------------------
        Lida Urbanek

              *                              Director                  September 25, 2000
-----------------------------
      H. Raymond Bingham

              *                              Director                  September 25, 2000
-----------------------------
       Robert T. Bond
</TABLE>


*By /s/ Stuart J. Nichols
   --------------------------
        Stuart J. Nichols
        Attorney-in-Fact


A majority of the members of the Board of Directors.



                                       7
<PAGE>   8
THE PLAN


Pursuant to the requirements of the Securities Act of 1933, the Registrant, as
the administrator of the KLA-Tencor 401(k) Plan, has duly caused this
registration statement to be signed on its behalf by the undersigned, thereunto
duly authorized, in the City of San Jose, State of California on the 25th day of
September, 2000.

KLA-TENCOR 401(k) PLAN
(Plan)

By   /s/ Kenneth L. Schroeder
   -------------------------------
         Kenneth L. Schroeder
President and Chief Executive Officer



                                       8
<PAGE>   9
                                  EXHIBIT INDEX


4.1      KLA-Tencor 401(k) Plan (July 1, 1997 Restatement), as amended by
         Amendments No. 1 through 4 thereto.

5.1.     Undertaking re Status of Favorable Determination Letter Covering the
         Plan. (See Item 8 of this Registration Statement).

23.1     Consent of PricewaterhouseCoopers LLP.

24.1     Power of Attorney of Directors.



                                       9
[{"type": "S-8", "sequence": "1", "filename": "f65854s-8.txt", "description": "FORM S-8", "secsgml_size_bytes": 17344}]
{"company-data": {"conformed-name": "KLA TENCOR CORP", "cik": "0000319201", "assigned-sic": "3827", "irs-number": "042564110", "state-of-incorporation": "DE", "fiscal-year-end": "0630"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-46598", "film-number": "728750"}, "business-address": {"street1": "160 RIO ROBLES", "city": "SAN JOSE", "state": "CA", "zip": "95134", "phone": "4084344200"}, "mail-address": {"street1": "160 RIO ROBLES", "city": "SAN JOSE", "state": "CA", "zip": "95161-9055"}, "former-company": {"former-conformed-name": "KLA INSTRUMENTS CORP", "date-changed": "19920703"}}
1
   As filed with the Securities and Exchange Commission on September 26, 2000

                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                    FORM S-8
                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933

                             ----------------------

                             KLA-TENCOR CORPORATION
             (Exact name of registrant as specified in its charter)

          Delaware                                     04-2564110
  (State or other jurisdiction             (I.R.S. Employer Identification No.)
of incorporation or organization)

                   160 Rio Robles, San Jose, California 95134
               (Address of principal executive offices) (Zip Code)

                             KLA-TENCOR 401(k) PLAN
                            (Full title of the plan)

                                Stuart J. Nichols
                       Vice President and General Counsel
                             KLA-Tencor Corporation
                   160 Rio Robles, San Jose, California 95134
                     (Name and address of agent for service)

   Telephone number, including area code, of agent for service: (408) 875-3000

                                   Copies to:

                             Larry W. Sonsini, Esq.
                          Christine L. Richardson, Esq.
                      Wilson Sonsini Goodrich & Rosati, PC
                               650 Page Mill Road
                           Palo Alto, California 94304

                                  CALCULATION OF REGISTRATION FEE
============================================================================================================
                                             Proposed Maximum       Proposed Maximum
Title of Securities to      Amount to be    Offering Price Per     Aggregate Offering       Amount of
    be Registered            Registered           Share*                 Price*         Registration Fee*
------------------------------------------------------------------------------------------------------------
Common Stock, $0.001 par   500,000 shares        $43.50                $21,750,000            $5,742
value**
============================================================================================================
*        Estimated solely for the purpose of calculating the registration fee
         pursuant to Rule 457(c) under the Securities Act of 1933, on the basis
         of $43.50 per share, the average of the high and low prices per share
         of the Common Stock on the NASDAQ National Market on September 22,
         2000.

**       Associated with the Common Stock are Common Stock Purchase Rights that
         will not be exercisable until the occurrence of certain prescribed
         events, none of which has occurred. In addition, pursuant to Rule
         416(c) under the Securities Act of 1933, this registration statement
         also covers an indeterminate amount of interests to be offered or sold
         pursuant to the KLA-Tencor 401(k) Plan described herein.
2
               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

ITEM 3. INCORPORATION OF DOCUMENTS BY REFERENCE

The following documents are incorporated by reference in this registration
statement: (i) the latest annual report of KLA-Tencor Corporation (the
"Registrant") filed pursuant to Section 13(a) or 15(d) of the Securities
Exchange Act of 1934, as amended (the "Exchange Act"); (ii) all other reports
filed by the Registrant pursuant to Section 13(a) or 15(d) of the Exchange Act
since the end of the fiscal year covered by the annual report referred to in
clause (i) above; and (iii) the description of the Registrant's common stock set
forth in the Registrant's Registration Statement on Form 8-A relating thereto,
including any amendment or report filed for the purpose of updating such
description. All documents filed by the Registrant or the KLA-Tencor 401(k)
Plan, as amended, after the date of this registration statement pursuant to
Sections 13(a), 13(c), 14, and 15(d) of the Exchange Act, prior to the filing of
a post-effective amendment (that indicates all securities offered have been sold
or deregisters all securities then remaining unsold), shall be deemed to be
incorporated by reference in this registration statement and to be a part hereof
from the date of filing of such documents.

ITEM 4. DESCRIPTION OF SECURITIES

Inapplicable.

ITEM 5. INTERESTS OF NAMED EXPERTS AND COUNSEL

Inapplicable.

ITEM 6. INDEMNIFICATION OF DIRECTORS AND OFFICERS

Section 145(a) of the Delaware General Corporation Law (the "DGCL") provides in
relevant part that "[a] corporation may indemnify any person who was or is a
party or is threatened to be made a party to any threatened, pending or
completed action, suit or proceeding, whether civil, criminal, administrative or
investigative (other than an action by or in the right of the corporation) by
reason of the fact that he is or was a director, officer, employee or agent of
the corporation, or is or was serving at the request of the corporation as a
director, officer, employee or agent of another corporation, partnership, joint
venture, trust or other enterprise, against expenses (including attorneys'
fees), judgments, fines and amounts paid in settlement actually and reasonably
incurred by him in connection with such action, suit or proceeding if he acted
in good faith and in a manner he reasonably believed to be in or not opposed to
the best interests of the corporation, and, with respect to any criminal action
or proceeding, had no reasonable cause to believe his conduct was unlawful."
With respect to derivative actions, Section 145(b) of the DGCL provides in
relevant part that "[a] corporation may indemnify any person who was or is a
party or is threatened to be made a party to any threatened, pending or
completed action or suit by or in the right of the corporation to procure a
judgment in its favor... [by reason of his service in one of the capacities
specified in the preceding sentence] against expenses (including attorneys'
fees) actually and reasonably incurred by him in connection with the defense or
settlement of such action or suit if he acted in good faith and in a manner he
reasonably believed to be in or not opposed to the best interests of the
corporation and except that no indemnification shall be made in respect of any
claim, issue or matter as to which such person shall have been

                                       2
3
adjudged to be liable to the corporation unless and only to the extent that the
Court of Chancery or the court in which such action or suit was brought shall
determine upon application that, despite the adjudication of liability but in
view of all the circumstances of the case, such person is fairly and reasonably
entitled to indemnity for such expenses which the Court of Chancery or such
other court shall deem proper."

The Registrant's Amended and Restated Certificate of Incorporation provides that
to the fullest extent permitted by the DGCL, no director of the Registrant shall
be personally liable to the Registrant or its stockholders for monetary damages
for breach of fiduciary duty as a director. The Amended and Restated Certificate
of Incorporation also provides that no amendment or repeal of such provision
shall apply to or have any effect on the right to indemnification permitted
thereunder with respect to claims arising from acts or omissions occurring in
whole or in part before the effective date of such amendment or repeal whether
asserted before or after such amendment or repeal.

The Registrant's Bylaws provide that the Registrant shall indemnify to the
fullest extent permitted by the DGCL each of its directors, officers, employees
and other agents against expenses actually and reasonably incurred in connection
with any proceeding arising by reason of the fact that such person is or was an
agent of the Registrant.

The Registrant has entered into indemnification agreements with its directors
and executive officers and intends to enter into indemnification agreements with
any new directors and executive officers in the future.

ITEM 7. EXEMPTION FROM REGISTRATION CLAIMED

Inapplicable.

ITEM 8. EXHIBITS

4.1      KLA-Tencor 401(k) Plan (July 1, 1997 Restatement), as amended by
         Amendments No. 1 through 4 thereto.

5.1      Undertaking re Status of Favorable Determination Letter Covering the
         Plan.

         The Registrant has received a favorable determination letter from the
         Internal Revenue Service (the "IRS") concerning the qualification of
         the KLA-Tencor 401(k) Plan (the "Plan") under Section 401(a) and
         related provisions of the Internal Revenue Code of 1986, as amended.
         The Registrant will submit any future material amendments to the Plan
         to the IRS with a request for a favorable determination that the Plan,
         as amended, continues to so qualify.

23.1     Consent of PricewaterhouseCoopers LLP.

24.1     Power of Attorney of Directors.

                                       3
4
ITEM 9. UNDERTAKINGS

         (a) The undersigned Registrant hereby undertakes:

                  (1) To file, during any period in which offers or sales are
being made, a post-effective amendment to this registration statement:

                           (i) To include any prospectus required by section
10(a)(3) of the Securities Act of 1933, as amended (the "Securities Act");

                           (ii) To reflect in the prospectus any facts or events
arising after the effective date of the registration statement (or the most
recent post-effective amendment thereof) which, individually or in the
aggregate, represent a fundamental change in the information set forth in the
registration statement;

                           (iii) To include any material information with
respect to the plan of distribution not previously disclosed in the registration
statement or any material change to such information in the registration
statement;

Provided, however, that paragraphs (a)(1)(i) and (a)(1)(ii) do not apply if the
information required to be included in a post-effective amendment by those
paragraphs is contained in periodic reports filed by the Registrant pursuant to
Section 13 or Section 15(d) of the Securities Exchange Act of 1934, as amended
(the "Exchange Act") that are incorporated by reference in the registration
statement.

                  (2) That, for the purpose of determining any liability under
the Securities Act each such post-effective amendment shall be deemed to be a
new registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof.

                  (3) To remove from registration by means of a post-effective
amendment any of the securities being registered which remain unsold at the
termination of the offering.

         (b) The undersigned Registrant hereby undertakes that, for purposes of
determining any liability under the Securities Act, each filing of the
Registrant's annual report pursuant to Section 13(a) or Section 15(d) of the
Exchange Act (and, where applicable, each filing of an employee benefit plan's
annual report pursuant to Section 15(d) of the Exchange Act) that is
incorporated by reference in the registration statement shall be deemed to be a
new registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof.

         (c) Insofar as indemnification for liabilities arising under the
Securities Act may be permitted to directors, officers and controlling persons
of the Registrant pursuant to the foregoing provisions, or otherwise, the
Registrant has been advised that in the opinion of the Securities and Exchange
Commission such indemnification is against public policy as expressed in the Act
and is, therefore, unenforceable. In the event that a claim for indemnification
against such liabilities (other than the payment by the Registrant of expenses
incurred or paid by a director, officer or controlling person of the Registrant
in the successful defense of any action, suit or proceeding) is asserted by such
director, officer or controlling person in connection with the securities being
registered, the Registrant will, unless in the opinion of its counsel the matter
has been settled by controlling precedent, submit to a court of appropriate
jurisdiction the

                                       4
5
question whether such indemnification by it is against public policy as
expressed in the Securities Act and will be governed by the final adjudication
of such issue.

                                       5
6
                                   Signatures

THE REGISTRANT

Pursuant to the requirements of the Securities Act of 1933, the Registrant
certifies that it has reasonable grounds to believe that it meets all of the
requirements for filing on Form S-8 and has duly caused this registration
statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the City of San Jose, State of California on the 25th day of
September, 2000.

KLA-TENCOR CORPORATION
(Registrant)

By /s/ Kenneth L. Schroeder
  ---------------------------
       Kenneth L. Schroeder
          President and
      Chief Executive Officer

Pursuant to the requirements of the Securities Act of 1933, this registration
statement has been signed by the following persons in the capacities and on the
dates indicated.
Signature                            Title                            Date
Principal Executive Officer:

   /s/ Kenneth L. Schroeder            President and Chief             September 25, 2000
-----------------------------          Executive Officer
       Kenneth L. Schroeder

Principal Financial and
  Accounting Officer:

   /s/ John Kispert                    Executive Vice President        September 25, 2000
-----------------------------          and Chief Financial Officer
       John Kispert
6
7

Directors:
*                        Chairman of the Board           September 25, 2000
-----------------------------              and Director
         Kenneth Levy

              *                              Director                  September 25, 2000
-----------------------------
    Kenneth L. Schroeder

              *                              Director                  September 25, 2000
-----------------------------
     Edward W. Barnholt

              *                              Director                  September 25, 2000
-----------------------------
    Richard J. Elkus, Jr.

              *                              Director                  September 25, 2000
-----------------------------
       Dean O. Morton

              *                              Director                  September 25, 2000
-----------------------------
       Jon D. Tompkins

              *                              Director                  September 25, 2000
-----------------------------
        Lida Urbanek

              *                              Director                  September 25, 2000
-----------------------------
      H. Raymond Bingham

              *                              Director                  September 25, 2000
-----------------------------
       Robert T. Bond
*By /s/ Stuart J. Nichols
   --------------------------
        Stuart J. Nichols
        Attorney-in-Fact

A majority of the members of the Board of Directors.

                                       7
8
THE PLAN

Pursuant to the requirements of the Securities Act of 1933, the Registrant, as
the administrator of the KLA-Tencor 401(k) Plan, has duly caused this
registration statement to be signed on its behalf by the undersigned, thereunto
duly authorized, in the City of San Jose, State of California on the 25th day of
September, 2000.

KLA-TENCOR 401(k) PLAN
(Plan)

By   /s/ Kenneth L. Schroeder
   -------------------------------
         Kenneth L. Schroeder
President and Chief Executive Officer

                                       8
9
                                  EXHIBIT INDEX

4.1      KLA-Tencor 401(k) Plan (July 1, 1997 Restatement), as amended by
         Amendments No. 1 through 4 thereto.

5.1.     Undertaking re Status of Favorable Determination Letter Covering the
         Plan. (See Item 8 of this Registration Statement).

23.1     Consent of PricewaterhouseCoopers LLP.

24.1     Power of Attorney of Directors.

                                       9