Exhibit 10.11

                             KLA-TENCOR CORPORATION

ADDENDUM TO KENNETH SCHROEDER AMENDED RETENTION AND NON-COMPETITION AGREEMENT



This Addendum (the  "Addendum") is made this 15th day of November,  2001, by and
between Kenneth L. Schroeder (the  "Executive") and KLA-Tencor  Corporation (the
"Company").

WHEREAS,  the Company and  Executive  have  previously  entered  into an Amended
Retention and  Non-Competition  Agreement (the  "Retention  and  Non-Competition
Agreement");
WHEREAS,  the parties  hereto desire to amend the Retention and  Non-Competition
Agreement to (i) provide  Executive with 100% vesting  acceleration in the event
of a  "double-trigger,"  and (ii) to modify  the  golden  parachute  excise  tax
provisions of the Retention and  Non-Competition  Agreement by  incorporating  a
$50,000 "hurdle" to provide greater protection for the Company;

NOW,  THEREFORE,  for good and valuable  consideration,  the receipt of which is
hereby acknowledged,  the Executive and the Company agree that the Retention and
Non-Competition Agreement is hereby amended as follows:

1. Double-Trigger Option Vesting Acceleration.  A new Section 21 is added to the
Retention and Non-Competition Agreement, providing:

"21.  Double-Trigger  Option Vesting  Acceleration.  If, on or after a Change of
Control (as defined herein),  Executive's employment with the Company terminates
due to (i) a voluntary  termination  for "Good Reason" (as defined  herein),  or
(ii) an  involuntary  termination  by the  Company  other than for  "Cause"  (as
defined in Section 7(b) hereof),  then,  subject to Executive  executing and not
revoking a Release  and not  breaching  the terms of  Section 10 hereof,  all of
Executive's  Company stock options shall  immediately  accelerate  vesting as to
100% of the then unvested shares.

For purposes of this Agreement, "Good Reason" means, without Executive's express
consent,

(i)  a  material   reduction  of  Executive's   duties,   title,   authority  or
responsibilities,   relative  to  Executive's   duties,   title,   authority  or
responsibilities  as in  effect  immediately  prior  to such  reduction,  or the
assignment   to  Executive  of  such  reduced   duties,   title,   authority  or
responsibilities,

(ii) a reduction  by the Company in the Base  Salary of  Executive  as in effect
immediately prior to such reduction;

(iii) a material  reduction  by the Company in the  aggregate  level of employee
benefits, or overall compensation,  including Target Bonuses, to which Executive
was  entitled   immediately  prior  to  such  reduction  with  the  result  that
Executive's  aggregate  benefits  package is  materially  reduced  (other than a
reduction that generally applies to Company  employees);

(iv)  the  relocation  of  Executive  to a  facility  or a  location  more  than
thirty-five (35) miles from Executive's then present  location;  or (vi) any act
or set of facts or  circumstances  which  would,  under  California  case law or
statute constitute a constructive termination of Executive.


For purposes of this Agreement, "Change of Control" shall mean the occurrence of
any of the following events:

(i) Any "person" (as such term is used in Sections 13(d) and 14(d) of the
Securities Exchange Act of 1934, as amended) becomes the "beneficial owner" (as
defined in Rule 13d-3 under said Act), directly or indirectly, of securities of
the Company representing fifty percent (50%) or more of the total voting power
represented by the Company's then outstanding voting securities; or

(ii) The consummation of the sale or disposition by the Company of all or
substantially all the Company's assets; or

(iii) The  consummation  of a merger or  consolidation  of the Company  with any
other  corporation,  other than a merger or consolidation  which would result in
the voting  securities  of the Company  outstanding  immediately  prior  thereto
continuing to represent  (either by remaining  outstanding or by being converted
into voting  securities of the surviving entity) at least fifty percent (50%) of
the total voting power  represented  by the voting  securities of the Company or
such   surviving   entity   outstanding   immediately   after  such   merger  or
consolidation; or

(iv) A change  in the  composition  of the  Board  occurring  within a  two-year
period,  as a  result  of which  fewer  than a  majority  of the  directors  are
Incumbent Directors.  "Incumbent  Directors" shall mean directors who either (A)
are  directors  of the  Company  as of the date upon which  this  Agreement  was
entered into, or (B) are elected,  or nominated for election,  to the Board with
the  affirmative  votes of at least a majority of those directors whose election
or  nomination  was  not  in  connection  with  any  transaction   described  in
subsections  (i),  (ii),  or (iii)  above,  or in  connection  with an actual or
threatened proxy contest relating to the election of directors to the Company."

2.  Golden   Parachute   Excise   Taxes.   Section  11  of  the   Retention  and
Non-Competition  Agreement is hereby  amended and replaced in its entirety  with
the following provision:


"11. Golden Parachute Excise Taxes.

(a) Parachute  Payments of Less than 3x Base Amount Plus Fifty Thousand Dollars.
In the event that the  benefits  provided  for in this  agreement  or  otherwise
payable to Executive (a) constitute  "parachute  payments" within the meaning of
Section 280G of the Internal Revenue Code of 1986, as amended (the "Code"),  (b)
would be subject to the excise tax imposed by Section 4999 of the Code,  and (c)
the aggregate value of such parachute payments, as determined in accordance with
Section 280G of the Code and the proposed  Treasury  Regulations  thereunder (or
the final Treasury Regulations, if they have then been adopted) is less than the
product  obtained by multiplying  three by Executive's  "base amount" within the
meaning of Code Section  280G(b)(3)  and adding to such product  fifty  thousand
dollars,  then such benefits shall be reduced to the extent  necessary (but only
to that  extent) so that no portion of such  benefits  will be subject to excise
tax under Section 4999 of the Code.

(b)  Parachute  Payments  Equal to or  Greater  than 3x Base  Amount  Plus Fifty
Thousand Dollars.  In the event that the benefits provided for in this agreement
or otherwise payable to Executive (a) constitute "parachute payments" within the
meaning  of  Section  280G of the Code,  (b) would be  subject to the excise tax
imposed  by  Section  4999 of the  Code,  and (c) the  aggregate  value  of such
parachute  payments,  as determined in accordance  with Section 280G of the Code
and  the  proposed  Treasury  Regulations  thereunder  (or  the  final  Treasury
Regulations,  if they have then been  adopted)  is equal to or greater  than the
product  obtained by multiplying  three by Executive's  "base amount" within the
meaning of Code Section  280G(b)(3)  and adding to such product  fifty  thousand
dollars, then the benefits shall be delivered in full.

(c) 280G Determinations. Unless the Company and the Executive otherwise agree in
writing,  the  determination of Executive's  excise tax liability and the amount
required to be paid or reduced under this Section 11 shall be made in writing by
the  Company's  independent  auditors  who are  primarily  used  by the  Company
immediately prior to the Change of Control (the "Accountants").  For purposes of
making the  calculations  required by this Section 11, the  Accountants may make
reasonable  assumptions and approximations  concerning  applicable taxes and may
rely on reasonable,  good faith  interpretations  concerning the  application of
Sections 280G and 4999 of the Code. The Company and the Executive  shall furnish
to the  Accountants  such  information  and  documents  as the  Accountants  may
reasonably  request in order to make a  determination  under this  Section.  The
Company shall bear all costs the Accountants may reasonably  incur in connection
with any calculations contemplated by this Section 11."

3. Retention and Non-Competition  Agreement. To the extent not expressly amended
hereby,  the Retention and  Non-Competition  Agreement remains in full force and
effect.

4. Entire  Agreement.  This  Addendum,  taken  together  with the  Retention and
Non-Competition  Agreement,  represents the entire  agreement of the parties and
shall supersede any and all previous  contracts,  arrangements or understandings
between the parties with respect to the subject matter hereof. This Addendum may
be amended at any time only by mutual written agreement of the parties hereto.






IN WITNESS WHEREOF, this Addendum has been entered into as of the date first set
forth above.

      KLA-TENCOR CORPORATION                         EXECUTIVE


By: /s/ KENNETH LEVY                           /s/ KENNETH L. SCHROEDER
   -------------------                         ------------------------


Date:November 15, 2001