Document:

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                                                                    EXHIBIT 10.3

                         NUMERICAL TECHNOLOGIES, INC.

                                1997 STOCK PLAN

                           (as amended and restated)

     1.   Purposes of the Plan.  The purposes of this Stock Plan are to
          --------------------
attract and retain the best available personnel for positions of substantial
responsibility, to provide additional incentive to Employees, Directors and
Consultants and to promote the success of the Company's business. Options
granted under the Plan may be Incentive Stock Options or Nonstatutory Stock
Options, as determined by the Administrator at the time of grant. Stock Purchase
Rights may also be granted under the Plan.

     2.   Definitions.  As used herein, the following definitions shall apply:
          -----------

          (a)  "Administrator" means the Board or any of its Committees as
               -------------
shall be administering the Plan in accordance with Section 4 hereof.

          (b)  "Applicable Laws" means the requirements relating to the
                ---------------
administration of stock option plans under U.S. state corporate laws, U.S.
federal and state securities laws, the Code, any stock exchange or quotation
system on which the Common Stock is listed or quoted and the applicable laws of
any other country or jurisdiction where Options or Stock Purchase Rights are
granted under the Plan.

          (c)  "Board" means the Board of Directors of the Company.
                -----

          (d)  "Code" means the Internal Revenue Code of 1986, as amended.
                ----

          (e)  "Committee"  means a committee of Directors appointed by the
                ---------
Board in accordance with Section 4 hereof.

          (f)  "Common Stock" means the Common Stock of the Company.
                ------------

          (g)  "Company" means Numerical Technologies, Inc., a California
                -------
corporation.

          (h)  "Consultant" means any person who is engaged by the Company or
                ----------
any Parent or Subsidiary to render consulting or advisory services to such
entity.

          (i)  "Director" means a member of the Board of Directors of the
                --------
Company.

          (j)  "Disability" means total and permanent disability as defined in
                ----------
Section 22(e)(3) of the Code.

          (k)  "Employee" means any person, including Officers and Directors,
                --------
employed by the Company or any Parent or Subsidiary of the Company. A Service
Provider shall not cease to be an Employee in the case of (i) any leave of
absence approved by the Company or (ii) transfers between locations of the
Company or between the Company, its Parent, any Subsidiary, or any
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successor. For purposes of Incentive Stock Options, no such leave may exceed
ninety days, unless reemployment upon expiration of such leave is guaranteed by
statute or contract. If reemployment upon expiration of a leave of absence
approved by the Company is not so guaranteed, on the 181st day of such leave any
Incentive Stock Option held by the Optionee shall cease to be treated as an
Incentive Stock Option and shall be treated for tax purposes as a Nonstatutory
Stock Option. Neither service as a Director nor payment of a director's fee by
the Company shall be sufficient to constitute "employment" by the Company.

          (l)  "Exchange Act" means the Securities Exchange Act of 1934, as
                ------------
amended.

          (m)  "Fair Market Value" means, as of any date, the value of Common
                -----------------
Stock determined as follows:

               (i)   If the Common Stock is listed on any established stock
exchange or a national market system, including without limitation the Nasdaq
National Market or The Nasdaq SmallCap Market of The Nasdaq Stock Market, its
Fair Market Value shall be the closing sales price for such stock (or the
closing bid, if no sales were reported) as quoted on such exchange or system for
the last market trading day prior to the time of determination, as reported in
The Wall Street Journal or such other source as the Administrator deems
reliable;

               (ii)  If the Common Stock is regularly quoted by a recognized
securities dealer but selling prices are not reported, its Fair Market Value
shall be the mean between the high bid and low asked prices for the Common Stock
on the last market trading day prior to the day of determination; or

               (iii) In the absence of an established market for the Common
Stock, the Fair Market Value thereof shall be determined in good faith by the
Administrator.

          (n)  "Incentive Stock Option" means an Option intended to qualify as
                ----------------------
an incentive stock option within the meaning of Section 422 of the Code.

          (o)  "Nonstatutory Stock Option" means an Option not intended to
                -------------------------
qualify as an Incentive Stock Option.

          (p)  "Officer" means a person who is an officer of the Company
                -------
within the meaning of Section 16 of the Exchange Act and the rules and
regulations promulgated thereunder.

          (q)  "Option" means a stock option granted pursuant to the Plan.
                ------

          (r)  "Option Agreement" means a written or electronic agreement
                ----------------
between the Company and an Optionee evidencing the terms and conditions of an
individual Option grant. The Option Agreement is subject to the terms and
conditions of the Plan.

          (s)  "Option Exchange Program" means a program whereby outstanding
                -----------------------
Options are exchanged for Options with a lower exercise price.

                                      -2-
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          (t)  "Optioned Stock" means the Common Stock subject to an Option or
                --------------
a Stock Purchase Right.

          (u)  "Optionee" means the holder of an outstanding Option or Stock
                --------
Purchase Right granted under the Plan.

          (v)  "Parent" means a "parent corporation," whether now or hereafter
                ------
existing, as defined in Section 424(e) of the Code.

          (w)  "Plan" means this 1997 Stock Plan.
                ----

          (x)  "Restricted Stock" means shares of Common Stock acquired
                ----------------
pursuant to a grant of a Stock Purchase Right under Section 11 below.

          (y)  "Section 16(b)" means Section 16(b) of the Securities Exchange
                -------------
Act of 1934, as amended.

          (z)  "Service Provider"  means an Employee, Director or Consultant.
                ----------------

          (aa) "Share" means a share of the Common Stock, as adjusted in
                -----
accordance with Section 12 below.

          (bb) "Stock Purchase Right" means a right to purchase Common Stock
                --------------------
pursuant to Section 11 below.

          (cc) "Subsidiary" means a "subsidiary corporation," whether now or
                ----------
hereafter existing, as defined in Section 424(f) of the Code.

     3.   Stock Subject to the Plan.  Subject to the provisions of Section 12 of
          -------------------------
the Plan, the maximum aggregate number of Shares which may be subject to option
and sold under the Plan is 4,131,000 Shares.  The Shares may be authorized but
unissued, or reacquired Common Stock.

     If an Option or Stock Purchase Right expires or becomes unexercisable
without having been exercised in full, or is surrendered pursuant to an Option
Exchange Program, the unpurchased Shares which were subject thereto shall become
available for future grant or sale under the Plan (unless the Plan has
terminated). However, Shares that have actually been issued under the Plan, upon
exercise of either an Option or Stock Purchase Right, shall not be returned to
the Plan and shall not become available for future distribution under the Plan,
except that if Shares of Restricted Stock are repurchased by the Company at
their original purchase price, such Shares shall become available for future
grant under the Plan.

     4.   Administration of the Plan.
          --------------------------

          (a)  Administrator.  The Plan shall be administered by the Board or a
               -------------
Committee appointed by the Board, which Committee shall be constituted to comply
with Applicable Laws.

                                      -3-
<PAGE>

          (b)  Powers of the Administrator.  Subject to the provisions of the
               ---------------------------
Plan and, in the case of a Committee, the specific duties delegated by the Board
to such Committee, and subject to the approval of any relevant authorities, the
Administrator shall have the authority in its discretion:

               (i)    to determine the Fair Market Value;

               (ii)   to select the Service Providers to whom Options and Stock
Purchase Rights may from time to time be granted hereunder;

               (iii)  to determine the number of Shares to be covered by each
such award granted hereunder;

               (iv)   to approve forms of agreement for use under the Plan;

               (v)    to determine the terms and conditions, of any Option or
Stock Purchase Right granted hereunder. Such terms and conditions include, but
are not limited to, the exercise price, the time or times when Options or Stock
Purchase Rights may be exercised (which may be based on performance criteria),
any vesting acceleration or waiver of forfeiture restrictions, and any
restriction or limitation regarding any Option or Stock Purchase Right or the
Common Stock relating thereto, based in each case on such factors as the
Administrator, in its sole discretion, shall determine;

               (vi)   to determine whether and under what circumstances an
Option may be settled in cash under subsection 9(e) instead of Common Stock;

               (vii)  to reduce the exercise price of any Option to the then
current Fair Market Value if the Fair Market Value of the Common Stock covered
by such Option has declined since the date the Option was granted;

               (viii) to initiate an Option Exchange Program;

               (ix)   to prescribe, amend and rescind rules and regulations
relating to the Plan, including rules and regulations relating to sub-plans
established for the purpose of qualifying for preferred tax treatment under
foreign tax laws;

               (x)    to allow Optionees to satisfy withholding tax obligations
by electing to have the Company withhold from the Shares to be issued upon
exercise of an Option or Stock Purchase Right that number of Shares having a
Fair Market Value equal to the amount required to be withheld. The Fair Market
Value of the Shares to be withheld shall be determined on the date that the
amount of tax to be withheld is to be determined. All elections by Optionees to
have Shares withheld for this purpose shall be made in such form and under such
conditions as the Administrator may deem necessary or advisable; and

               (xi)   to construe and interpret the terms of the Plan and awards
granted pursuant to the Plan.

                                      -4-
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          (c)  Effect of Administrator's Decision.  All decisions,
               ----------------------------------
determinations and interpretations of the Administrator shall be final and
binding on all Optionees.

     5.   Eligibility.
          -----------

          (a)  Nonstatutory Stock Options and Stock Purchase Rights may be
granted to Service Providers. Incentive Stock Options may be granted only to
Employees.

          (b)  Each Option shall be designated in the Option Agreement as either
an Incentive Stock Option or a Nonstatutory Stock Option. However,
notwithstanding such designation, to the extent that the aggregate Fair Market
Value of the Shares with respect to which Incentive Stock Options are
exercisable for the first time by the Optionee during any calendar year (under
all plans of the Company and any Parent or Subsidiary) exceeds $100,000, such
Options shall be treated as Nonstatutory Stock Options. For purposes of this
Section 5(b), Incentive Stock Options shall be taken into account in the order
in which they were granted. The Fair Market Value of the Shares shall be
determined as of the time the Option with respect to such Shares is granted.

          (c)  Neither the Plan nor any Option or Stock Purchase Right shall
confer upon any Optionee any right with respect to continuing the Optionee's
relationship as a Service Provider with the Company, nor shall it interfere in
any way with his or her right or the Company's right to terminate such
relationship at any time, with or without cause.

     6.   Term of Plan.  The Plan shall become effective upon its adoption by
          ------------
the Board. It shall continue in effect for a term of ten (10) years unless
sooner terminated under Section 14 of the Plan.

     7.   Term of Option.  The term of each Option shall be stated in the Option
          --------------
Agreement; provided, however, that the term shall be no more than ten (10) years
from the date of grant thereof.  In the case of an Incentive Stock Option
granted to an Optionee who, at the time the Option is granted, owns stock
representing more than ten percent (10%) of the voting power of all classes of
stock of the Company or any Parent or Subsidiary, the term of the Option shall
be five (5) years from the date of grant or such shorter term as may be provided
in the Option Agreement.

     8.   Option Exercise Price and Consideration.
          ---------------------------------------

          (a)  The per share exercise price for the Shares to be issued upon
exercise of an Option shall be such price as is determined by the Administrator,
but shall be subject to the following:

               (i)  In the case of an Incentive Stock Option

                    (A)  granted to an Employee who, at the time of grant of
such Option, owns stock representing more than ten percent (10%) of the voting
power of all classes of stock of the Company or any Parent or Subsidiary, the
exercise price shall be no less than 110% of the Fair Market Value per Share on
the date of grant.

                                      -5-
<PAGE>

                     (B)  granted to any other Employee, the per Share exercise
price shall be no less than 100% of the Fair Market Value per Share on the date
of grant.

               (ii)  In the case of a Nonstatutory Stock Option

                     (A)  granted to a Service Provider who, at the time of
grant of such Option, owns stock representing more than ten percent (10%) of the
voting power of all classes of stock of the Company or any Parent or Subsidiary,
the exercise price shall be no less than 110% of the Fair Market Value per Share
on the date of grant.

                     (B)  granted to any other Service Provider, the per Share
exercise price shall be no less than 85% of the Fair Market Value per Share on
the date of grant.

               (iii) Notwithstanding the foregoing, Options may be granted with
a per Share exercise price other than as required above pursuant to a merger or
other corporate transaction.

          (b)  The consideration to be paid for the Shares to be issued upon
exercise of an Option, including the method of payment, shall be determined by
the Administrator (and, in the case of an Incentive Stock Option, shall be
determined at the time of grant). Such consideration may consist of (1) cash,
(2) check, (3) promissory note, (4) other Shares which (x) in the case of Shares
acquired upon exercise of an Option, have been owned by the Optionee for more
than six months on the date of surrender, and (y) have a Fair Market Value on
the date of surrender equal to the aggregate exercise price of the Shares as to
which such Option shall be exercised, (5) consideration received by the Company
under a cashless exercise program implemented by the Company in connection with
the Plan, or (6) any combination of the foregoing methods of payment. In making
its determination as to the type of consideration to accept, the Administrator
shall consider if acceptance of such consideration may be reasonably expected to
benefit the Company.

     9.   Exercise of Option.
          ------------------

          (a)  Procedure for Exercise; Rights as a Shareholder. Any Option
               -----------------------------------------------
granted hereunder shall be exercisable according to the terms hereof at such
times and under such conditions as determined by the Administrator and set forth
in the Option Agreement. Except in the case of Options granted to Officers,
Directors and Consultants, Options shall become exercisable at a rate of no less
than 20% per year over five (5) years from the date the Options are granted.
Unless the Administrator provides otherwise, vesting of Options granted
hereunder shall be tolled during any unpaid leave of absence. An Option may not
be exercised for a fraction of a Share.

          An Option shall be deemed exercised when the Company receives: (i)
written or electronic notice of exercise (in accordance with the Option
Agreement) from the person entitled to exercise the Option, and (ii) full
payment for the Shares with respect to which the Option is exercised.  Full
payment may consist of any consideration and method of payment authorized by the
Administrator and permitted by the Option Agreement and the Plan.  Shares issued
upon exercise of an Option shall be issued in the name of the Optionee or, if
requested by the Optionee, in the name of the Optionee and his or her spouse.
Until the Shares are issued (as evidenced by the appropriate entry on the books
of the Company or of a duly authorized transfer agent of the Company), no right

                                      -6-
<PAGE>

to vote or receive dividends or any other rights as a shareholder shall exist
with respect to the Shares, notwithstanding the exercise of the Option.  The
Company shall issue (or cause to be issued) such Shares promptly after the
Option is exercised.  No adjustment will be made for a dividend or other right
for which the record date is prior to the date the Shares are issued, except as
provided in Section 12 of the Plan.

          Exercise of an Option in any manner shall result in a decrease in the
number of Shares thereafter available, both for purposes of the Plan and for
sale under the Option, by the number of Shares as to which the Option is
exercised.

          (b)  Termination of Relationship as a Service Provider.  If an
               -------------------------------------------------
Optionee ceases to be a Service Provider, such Optionee may exercise his or her
Option within such period of time as is specified in the Option Agreement (of at
least thirty (30) days) to the extent that the Option is vested on the date of
termination (but in no event later than the expiration of the term of the Option
as set forth in the Option Agreement). In the absence of a specified time in the
Option Agreement, the Option shall remain exercisable for three (3) months
following the Optionee's termination. If, on the date of termination, the
Optionee is not vested as to his or her entire Option, the Shares covered by the
unvested portion of the Option shall revert to the Plan. If, after termination,
the Optionee does not exercise his or her Option within the time specified by
the Administrator, the Option shall terminate, and the Shares covered by such
Option shall revert to the Plan.

          (c)  Disability of Optionee.  If an Optionee ceases to be a Service
               ----------------------
Provider as a result of the Optionee's Disability, the Optionee may exercise his
or her Option within such period of time as is specified in the Option Agreement
(of at least six (6) months) to the extent the Option is vested on the date of
termination (but in no event later than the expiration of the term of such
Option as set forth in the Option Agreement). In the absence of a specified time
in the Option Agreement, the Option shall remain exercisable for twelve (12)
months following the Optionee's termination. If, on the date of termination, the
Optionee is not vested as to his or her entire Option, the Shares covered by the
unvested portion of the Option shall revert to the Plan. If, after termination,
the Optionee does not exercise his or her Option within the time specified
herein, the Option shall terminate, and the Shares covered by such Option shall
revert to the Plan.

          (d)  Death of Optionee.  If an Optionee dies while a Service Provider,
               -----------------
the Option may be exercised within such period of time as is specified in the
Option Agreement (of at least six (6) months) to the extent that the Option is
vested on the date of death (but in no event later than the expiration of the
term of such Option as set forth in the Option Agreement) by the Optionee's
estate or by a person who acquires the right to exercise the Option by bequest
or inheritance. In the absence of a specified time in the Option Agreement, the
Option shall remain exercisable for twelve (12) months following the Optionee's
termination. If, at the time of death, the Optionee is not vested as to the
entire Option, the Shares covered by the unvested portion of the Option shall
immediately revert to the Plan. If the Option is not so exercised within the
time specified herein, the Option shall terminate, and the Shares covered by
such Option shall revert to the Plan.

          (e)  Buyout Provisions.  The Administrator may at any time offer to
               -----------------
buy out for a payment in cash or Shares, an Option previously granted, based on
such terms and conditions as the Administrator shall establish and communicate
to the Optionee at the time that such offer is made.

                                      -7-
<PAGE>

     10.  Non-Transferability of Options and Stock Purchase Rights.  The Options
          --------------------------------------------------------
and Stock Purchase Rights may not be sold, pledged, assigned, hypothecated,
transferred, or disposed of in any manner other than by will or by the laws of
descent or distribution and may be exercised, during the lifetime of the
Optionee, only by the Optionee.

     11.  Stock Purchase Rights.
          ---------------------

          (a)  Rights to Purchase.  Stock Purchase Rights may be issued either
               ------------------
alone, in addition to, or in tandem with other awards granted under the Plan
and/or cash awards made outside of the Plan. After the Administrator determines
that it will offer Stock Purchase Rights under the Plan, it shall advise the
offeree in writing or electronically of the terms, conditions and restrictions
related to the offer, including the number of Shares that such person shall be
entitled to purchase, the price to be paid, and the time within which such
person must accept such offer. The terms of the offer shall comply in all
respects with Section 260.140.42 of Title 10 of the California Code of
Regulations. The offer shall be accepted by execution of a Restricted Stock
purchase agreement in the form determined by the Administrator.

          (b)  Repurchase Option.  Unless the Administrator determines
               -----------------
otherwise, the Restricted Stock purchase agreement shall grant the Company a
repurchase option exercisable upon the voluntary or involuntary termination of
the purchaser's service with the Company for any reason (including death or
disability). The purchase price for Shares repurchased pursuant to the
Restricted Stock purchase agreement shall be the original price paid by the
purchaser and may be paid by cancellation of any indebtedness of the purchaser
to the Company. The repurchase option shall lapse at such rate as the
Administrator may determine. Except with respect to Shares purchased by
Officers, Directors and Consultants, the repurchase option shall in no case
lapse at a rate of less than 20% per year over five (5) years from the date of
purchase.

          (c)  Other Provisions.  The Restricted Stock purchase agreement shall
               ----------------
contain such other terms, provisions and conditions not inconsistent with the
Plan as may be determined by the Administrator in its sole discretion.

          (d)  Rights as a Shareholder.  Once the Stock Purchase Right is
               -----------------------
exercised, the purchaser shall have rights equivalent to those of a shareholder
and shall be a shareholder when his or her purchase is entered upon the records
of the duly authorized transfer agent of the Company. No adjustment shall be
made for a dividend or other right for which the record date is prior to the
date the Stock Purchase Right is exercised, except as provided in Section 12 of
the Plan.

     12.  Adjustments Upon Changes in Capitalization, Merger or Asset Sale.
          ----------------------------------------------------------------

          (a)  Changes in Capitalization.  Subject to any required action by the
               -------------------------
shareholders of the Company, the number of shares of Common Stock covered by
each outstanding Option or Stock Purchase Right, and the number of shares of
Common Stock which have been authorized for issuance under the Plan but as to
which no Options or Stock Purchase Rights have yet been granted or which have
been returned to the Plan upon cancellation or expiration of an Option or Stock
Purchase Right, as well as the price per share of Common Stock covered by each
such outstanding Option or Stock Purchase Right, shall be proportionately
adjusted for any increase or decrease in the

                                      -8-
<PAGE>

number of issued shares of Common Stock resulting from a stock split, reverse
stock split, stock dividend, combination or reclassification of the Common
Stock, or any other increase or decrease in the number of issued shares of
Common Stock effected without receipt of consideration by the Company. The
conversion of any convertible securities of the Company shall not be deemed to
have been "effected without receipt of consideration." Such adjustment shall be
made by the Board, whose determination in that respect shall be final, binding
and conclusive. Except as expressly provided herein, no issuance by the Company
of shares of stock of any class, or securities convertible into shares of stock
of any class, shall affect, and no adjustment by reason thereof shall be made
with respect to, the number or price of shares of Common Stock subject to an
Option or Stock Purchase Right.

          (b)  Dissolution or Liquidation.  In the event of the proposed
               --------------------------
dissolution or liquidation of the Company, the Administrator shall notify each
Optionee as soon as practicable prior to the effective date of such proposed
transaction. The Administrator in its discretion may provide for an Optionee to
have the right to exercise his or her Option or Stock Purchase Right until
fifteen (15) days prior to such transaction as to all of the Optioned Stock
covered thereby, including Shares as to which the Option or Stock Purchase Right
would not otherwise be exercisable. In addition, the Administrator may provide
that any Company repurchase option applicable to any Shares purchased upon
exercise of an Option or Stock Purchase Right shall lapse as to all such Shares,
provided the proposed dissolution or liquidation takes place at the time and in
the manner contemplated. To the extent it has not been previously exercised, an
Option or Stock Purchase Right will terminate immediately prior to the
consummation of such proposed action.

          (c)  Merger or Asset Sale.  In the event of a merger of the Company
               --------------------
with or into another corporation, or the sale of substantially all of the assets
of the Company, each outstanding Option and Stock Purchase Right shall be
assumed or an equivalent option or right substituted by the successor
corporation or a Parent or Subsidiary of the successor corporation. In the event
that the successor corporation refuses to assume or substitute for the Option or
Stock Purchase Right, the Option or Stock Purchase Right shall terminate as of
the date of the closing of the merger or asset sale. For the purposes of this
paragraph, the Option or Stock Purchase Right shall be considered assumed if,
following the merger or sale of assets, the option or right confers the right to
purchase or receive, for each Share of Optioned Stock subject to the Option or
Stock Purchase Right immediately prior to the merger or sale of assets, the
consideration (whether stock, cash, or other securities or property) received in
the merger or sale of assets by holders of Common Stock for each Share held on
the effective date of the transaction (and if holders were offered a choice of
consideration, the type of consideration chosen by the holders of a majority of
the outstanding Shares); provided, however, that if such consideration received
in the merger or sale of assets is not solely common stock of the successor
corporation or its Parent, the Administrator may, with the consent of the
successor corporation, provide for the consideration to be received upon the
exercise of the Option or Stock Purchase Right, for each Share of Optioned Stock
subject to the Option or Stock Purchase Right, to be solely common stock of the
successor corporation or its Parent equal in fair market value to the per share
consideration received by holders of Common Stock in the merger or sale of
assets.

     13.  Time of Granting Options and Stock Purchase Rights.  The date of
          --------------------------------------------------
grant of an Option or Stock Purchase Right shall, for all purposes, be the date
on which the Administrator makes the

                                      -9-
<PAGE>

determination granting such Option or Stock Purchase Right, or such other date
as is determined by the Administrator. Notice of the determination shall be
given to each Employee to whom an Option or Stock Purchase Right is so granted
within a reasonable time after the date of such grant.

     14.  Amendment and Termination of the Plan.
          -------------------------------------

          (a)  Amendment and Termination.  The Board may at any time amend,
               -------------------------
alter, suspend or terminate the Plan.

          (b)  Shareholder Approval.  The Board shall obtain shareholder
               --------------------
approval of any Plan amendment to the extent necessary and desirable to comply
with Applicable Laws.

          (c)  Effect of Amendment or Termination.  No amendment, alteration,
               ----------------------------------
suspension or termination of the Plan shall impair the rights of any Optionee,
unless mutually agreed otherwise between the Optionee and the Administrator,
which agreement must be in writing and signed by the Optionee and the Company.
Termination of the Plan shall not affect the Administrator's ability to exercise
the powers granted to it hereunder with respect to Options granted under the
Plan prior to the date of such termination.

     15.  Conditions Upon Issuance of Shares.
          ----------------------------------

          (a)  Legal Compliance.  Shares shall not be issued pursuant to the
               ----------------
exercise of an Option unless the exercise of such Option and the issuance and
delivery of such Shares shall comply with Applicable Laws and shall be further
subject to the approval of counsel for the Company with respect to such
compliance.

          (b)  Investment Representations.  As a condition to the exercise of an
               --------------------------
Option, the Administrator may require the person exercising such Option to
represent and warrant at the time of any such exercise that the Shares are being
purchased only for investment and without any present intention to sell or
distribute such Shares if, in the opinion of counsel for the Company, such a
representation is required.

     16.  Inability to Obtain Authority.  The inability of the Company to obtain
          -----------------------------
authority from any regulatory body having jurisdiction, which authority is
deemed by the Company's counsel to be necessary to the lawful issuance and sale
of any Shares hereunder, shall relieve the Company of any liability in respect
of the failure to issue or sell such Shares as to which such requisite authority
shall not have been obtained.

     17.  Reservation of Shares.  The Company, during the term of this Plan,
          ---------------------
shall at all times reserve and keep available such number of Shares as shall be
sufficient to satisfy the requirements of the Plan.

     18.  Shareholder Approval.  The Plan shall be subject to approval by the
          --------------------
shareholders of the Company within twelve (12) months after the date the Plan is
adopted.  Such shareholder approval shall be obtained in the degree and manner
required under Applicable Laws.

                                      -10-
<PAGE>

     19.  Information to Optionees and Purchasers.  The Company shall provide to
          ---------------------------------------
each Optionee and to each individual who acquires Shares pursuant to the Plan,
not less frequently than annually during the period such Optionee or purchaser
has one or more Options or Stock Purchase Rights outstanding, and, in the case
of an individual who acquires Shares pursuant to the Plan, during the period
such individual owns such Shares, copies of annual financial statements.  The
Company shall not be required to provide such statements to key employees whose
duties in connection with the Company assure their access to equivalent
information.

                                      -11-
<PAGE>

                         NUMERICAL TECHNOLOGIES, INC.

                                1997 STOCK PLAN

                   STOCK OPTION AGREEMENT -- EARLY EXERCISE

     Unless otherwise defined herein, the terms defined in the Plan shall have
the same defined meanings in this Option Agreement.

I.   NOTICE OF STOCK OPTION GRANT
     ----------------------------

     [Optionee's Name]

     You have been granted an option to purchase Common Stock of the Company,
subject to the terms and conditions of the Plan and this Option Agreement, as
follows:

     Date of Grant:                     ________________________________

     Vesting Commencement Date:         ________________________________

     Exercise Price per Share:          $_______________________________

     Total Number of Shares Granted:    ________________________________

     Total Exercise Price:              $_______________________________

     Type of Option:                    ____  Incentive Stock Option

                                        ____  Nonstatutory Stock Option

     Term/Expiration Date:              Ten Years/________________*

_______________
*  Or earlier, pursuant to the termination period set forth below.

     Exercise and Vesting Schedule:
     -----------------------------

     This Option is exercisable immediately, in whole or in part, and shall vest
according to the following vesting schedule:

     The vesting schedule shall be determined by the Administrator in its sole
discretion.
<PAGE>

     Termination Period:
     ------------------

     You may exercise this Option for thirty days after you cease to be a
Service Provider. Upon your death or disability, this Option may be exercised
for one year after you cease to be a Service Provider. In no event may you
exercise this Option after the Term/Expiration Date as provided above.

II.  AGREEMENT
     ---------

     1.   Grant of Option.  The Plan Administrator of the Company hereby grants
          ---------------
to the Optionee named in the Notice of Grant (the "Optionee"), an option (the
"Option") to purchase the number of Shares set forth in the Notice of Grant, at
the exercise price per Share set forth in the Notice of Grant (the "Exercise
Price"), and subject to the terms and conditions of the Plan, which is
incorporated herein by reference. Subject to Section 14(c) of the Plan, in the
event of a conflict between the terms and conditions of the Plan and this Option
Agreement, the terms and conditions of the Plan shall prevail.

     If designated in the Notice of Grant as an Incentive Stock Option ("ISO"),
this Option is intended to qualify as an Incentive Stock Option as defined in
Section 422 of the Code. Nevertheless, to the extent that it exceeds the
$100,000 rule of Code Section 422(d), this Option shall be treated as a
Nonstatutory Stock Option ("NSO").

     2.   Exercise of Option.  This Option shall be exercisable during its
          ------------------
term in accordance with the provisions of Section 9 of the Plan as follows:

          (a)  Right to Exercise.
               -----------------

               (i)   Subject to subsections 2(a)(ii) and 2(a)(iii) below, this
Option shall be exercisable cumulatively according to the vesting schedule set
forth in the Notice of Grant. Alternatively, at the election of the Optionee,
this option may be exercised in whole or in part at any time as to Shares which
have not yet vested. For purposes of this Stock Option Agreement, Shares subject
to the Option shall vest based on continued employment of Optionee with the
Company. Vested Shares shall not be subject to the Company's repurchase right
(as set forth in the Restricted Stock Purchase Agreement, attached hereto as
Exhibit C-1).
-----------

               (ii)  As a condition to exercising this Option for unvested
Shares, the Optionee shall execute the Restricted Stock Purchase Agreement.

               (iii) This Option may not be exercised for a fraction of a Share.

          (b)  Method of Exercise.  This Option shall be exercisable by delivery
               ------------------
of an exercise notice in the form attached as Exhibit A (the "Exercise Notice")
                                              ---------
which shall state the election to exercise the Option, the number of Shares with
respect to which the Option is being exercised, and such other representations
and agreements as may be required by the Company. The Exercise Notice shall be
accompanied by payment of the aggregate Exercise Price as to all Exercised

                                      -2-
<PAGE>

Shares. This Option shall be deemed to be exercised upon receipt by the Company
of such fully executed Exercise Notice accompanied by the aggregate Exercise
Price.

     No Shares shall be issued pursuant to the exercise of an Option unless such
issuance and such exercise complies with Applicable Laws.  Assuming such
compliance, for income tax purposes the Shares shall be considered transferred
to the Optionee on the date on which the Option is exercised with respect to
such Shares.

     3.   Optionee's Representations.  In the event the Shares have not been
          --------------------------
registered under the Securities Act of 1933, as amended, at the time this Option
is exercised, the Optionee shall, if required by the Company, concurrently with
the exercise of all or any portion of this Option, deliver to the Company his or
her Investment Representation Statement in the form attached hereto as Exhibit
                                                                       -------
B.

     4.   Lock-Up Period.  Optionee hereby agrees that, if so requested by the
          --------------
Company or any representative of the underwriters (the "Managing Underwriter")
in connection with any registration of the offering of any securities of the
Company under the Securities Act, Optionee shall not sell or otherwise transfer
any Shares or other securities of the Company during the 180-day period (or such
other period as may be requested in writing by the Managing Underwriter and
agreed to in writing by the Company) (the "Market Standoff Period") following
the effective date of a registration statement of the Company filed under the
Securities Act.  Such restriction shall apply only  to the first registration
statement of the Company to become effective under the Securities Act that
includes securities to be sold on behalf of the Company to the public in an
underwritten public offering under the Securities Act.  The Company may impose
stop-transfer instructions with respect to securities subject to the foregoing
restrictions until the end of such Market Standoff Period.

     5.   Method of Payment.  Payment of the aggregate Exercise Price shall be
          -----------------
by any of the following, or a combination thereof, at the election of the
Optionee:

          (a)  cash;

          (b)  check;

          (c)  consideration received by the Company under a formal cashless
exercise program adopted by the Company in connection with the Plan; or

          (d)  surrender of other Shares which, (i) in the case of Shares
acquired upon exercise of an option, have been owned by the Optionee for more
than six (6) months on the date of surrender, and (ii) have a Fair Market Value
on the date of surrender equal to the aggregate Exercise Price of the Exercised
Shares.

     6.   Restrictions on Exercise.  This Option may not be exercised until such
          ------------------------
time as the Plan has been approved by the shareholders of the Company, or if the
issuance of such Shares upon such exercise or the method of payment of
consideration for such shares would constitute a violation of any Applicable
Law.

                                      -3-
<PAGE>

     7.   Non-Transferability of Option.  This Option may not be transferred
          -----------------------------
in any manner otherwise than by will or by the laws of descent or distribution
and may be exercised during the lifetime of Optionee only by Optionee. The terms
of the Plan and this Option Agreement shall be binding upon the executors,
administrators, heirs, successors and assigns of the Optionee.

     8.   Term of Option.  This Option may be exercised only within the term set
          --------------
out in the Notice of Grant, and may be exercised during such term only in
accordance with the Plan and the terms of this Option.

     9.   Tax Consequences.  Set forth below is a brief summary as of the date
          ----------------
of this Option of some of the federal tax consequences of exercise of this
Option and disposition of the Shares. THIS SUMMARY IS NECESSARILY INCOMPLETE,
AND THE TAX LAWS AND REGULATIONS ARE SUBJECT TO CHANGE. THE OPTIONEE SHOULD
CONSULT A TAX ADVISER BEFORE EXERCISING THIS OPTION OR DISPOSING OF THE SHARES.

          (a)  Exercise of ISO.  If this Option qualifies as an ISO, there will
               ---------------
be no regular federal income tax liability upon the exercise of the Option,
although the excess, if any, of the Fair Market Value of the Shares on the date
of exercise over the Exercise Price will be treated as an adjustment to the
alternative minimum tax for federal tax purposes and may subject the Optionee to
the alternative minimum tax in the year of exercise.

          (b)  Exercise of ISO Following Disability.  If the Optionee ceases to
               ------------------------------------
be an Employee as a result of a disability that is not a total and permanent
disability as defined in Section 22(e)(3) of the Code, to the extent permitted
on the date of termination, the Optionee must exercise an ISO within three
months of such termination for the ISO to be qualified as an ISO.

          (c)  Exercise of Nonstatutory Stock Option.  There may be a regular
               -------------------------------------
federal income tax liability upon the exercise of a Nonstatutory Stock Option.
The Optionee will be treated as having received compensation income (taxable at
ordinary income tax rates) equal to the excess, if any, of the Fair Market Value
of the Shares on the date of exercise over the Exercise Price. If Optionee is an
Employee or a former Employee, the Company will be required to withhold from
Optionee's compensation or collect from Optionee and pay to the applicable
taxing authorities an amount in cash equal to a percentage of this compensation
income at the time of exercise, and may refuse to honor the exercise and refuse
to deliver Shares if such withholding amounts are not delivered at the time of
exercise.

          (d)  Disposition of Shares.  In the case of an NSO, if Shares are
               ---------------------
held for at least one year, any gain realized on disposition of the Shares will
be treated as long-term capital gain for federal income tax purposes. In the
case of an ISO, if Shares transferred pursuant to the Option are held for at
least one year after exercise and at least two years after the Date of Grant,
any gain realized on disposition of the Shares will also be treated as long-term
capital gain for federal income tax purposes. If Shares purchased under an ISO
are disposed of within one year after exercise or two years after the Date of
Grant, any gain realized on such disposition will be treated as compensation
income (taxable at ordinary income rates) to the extent of the difference
between the Exercise Price and the lesser of (i) the Fair Market Value of the
Shares on the date of exercise, or (ii) the sale price

                                      -4-
<PAGE>

of the Shares. Any additional gain will be taxed as capital gain, short-term
depending on the period that the ISO Shares were held.

          (e)  Notice of Disqualifying Disposition of ISO Shares.  If the Option
               -------------------------------------------------
granted to Optionee herein is an ISO, and if Optionee sells or otherwise
disposes of any of the Shares acquired pursuant to the ISO on or before the
later of (i) the date two years after the Date of Grant, or (ii) the date one
year after the date of exercise, the Optionee shall immediately notify the
Company in writing of such disposition.  Optionee agrees that Optionee may be
subject to income tax withholding by the Company on the compensation income
recognized by the Optionee.

          (f)  Section 83(b) Election for Unvested Shares Purchased Pursuant to
               ----------------------------------------------------------------
Options.  With respect to the exercise of an Option for unvested Shares, an
-------
election may be filed by the Optionee with the Internal Revenue Service, within
                                                                         ------
30 days of the purchase of the Shares, electing pursuant to Section 83(b) of the
-------
Code to be taxed currently on any difference between the purchase price of the
Shares and their Fair Market Value on the date of purchase.  In the case of a
Nonstatutory Stock Option, this will result in a recognition of taxable income
to the Optionee on the date of exercise, measured by the excess, if any, of the
fair market value of the Shares, at the time the Option is exercised over the
purchase price for the Shares.  Absent such an election, taxable income will be
measured and recognized by Optionee at the time or times on which the Company's
Repurchase Option lapses.  In the case of an Incentive Stock Option, such an
election will result in a recognition of income to the Optionee for alternative
minimum tax purposes on the date of exercise, measured by the excess, if any, of
the fair market value of the Shares, at the time the option is exercised, over
the purchase price for the Shares.  Absent such an election, alternative minimum
taxable income will be measured and recognized by Optionee at the time or times
on which the Company's Repurchase Option lapses.   Optionee is strongly
encouraged to seek the advice of his or her own tax consultants in connection
with the purchase of the Shares and the advisability of filing of the Election
under Section 83(b) of the Code.  A form of Election under Section 83(b) is
attached hereto as Exhibit C-5 for reference.
                   -----------

     OPTIONEE ACKNOWLEDGES THAT IT IS OPTIONEE'S SOLE RESPONSIBILITY AND NOT THE
COMPANY'S TO FILE TIMELY THE ELECTION UNDER SECTION 83(b), EVEN IF OPTIONEE
REQUESTS THE COMPANY OR ITS REPRESENTATIVE TO MAKE THIS FILING ON OPTIONEE'S
BEHALF.

     10.  Entire Agreement; Governing Law.  The Plan is incorporated herein by
          -------------------------------
reference.  The Plan and this Option Agreement constitute the entire agreement
of the parties with respect to the subject matter hereof and supersede in their
entirety all prior undertakings and agreements of the Company and Optionee with
respect to the subject matter hereof, and may not be modified adversely to the
Optionee's interest except by means of a writing signed by the Company and
Optionee.  This agreement is governed by the internal substantive laws but not
the choice of law rules of California.

     11.  No Guarantee of Continued Service.  OPTIONEE ACKNOWLEDGES AND AGREES
          ---------------------------------
THAT THE VESTING OF SHARES PURSUANT TO THE VESTING SCHEDULE HEREOF IS EARNED
ONLY BY CONTINUING AS A SERVICE PROVIDER AT THE WILL OF THE COMPANY (NOT THROUGH
THE ACT OF BEING HIRED, BEING GRANTED THIS

                                      -5-
<PAGE>

OPTION OR ACQUIRING SHARES HEREUNDER). OPTIONEE FURTHER ACKNOWLEDGES AND AGREES
THAT THIS AGREEMENT, THE TRANSACTIONS CONTEMPLATED HEREUNDER AND THE VESTING
SCHEDULE SET FORTH HEREIN DO NOT CONSTITUTE AN EXPRESS OR IMPLIED PROMISE OF
CONTINUED ENGAGEMENT AS A SERVICE PROVIDER FOR THE VESTING PERIOD, FOR ANY
PERIOD, OR AT ALL, AND SHALL NOT INTERFERE IN ANY WAY WITH OPTIONEE'S RIGHT OR
THE COMPANY'S RIGHT TO TERMINATE OPTIONEE'S RELATIONSHIP AS A SERVICE PROVIDER
AT ANY TIME, WITH OR WITHOUT CAUSE.

     Optionee acknowledges receipt of a copy of the Plan and represents that he
or she is familiar with the terms and provisions thereof, and hereby accepts
this Option subject to all of the terms and provisions thereof. Optionee has
reviewed the Plan and this Option in their entirety, has had an opportunity to
obtain the advice of counsel prior to executing this Option and fully
understands all provisions of the Option. Optionee hereby agrees to accept as
binding, conclusive and final all decisions or interpretations of the
Administrator upon any questions arising under the Plan or this Option. Optionee
further agrees to notify the Company upon any change in the residence address
indicated below.

OPTIONEE:                          NUMERICAL TECHNOLOGIES, INC.

_______________________________    _______________________________
Signature                          By

_______________________________    _______________________________
Print Name                         Title

_______________________________
_______________________________
Residence Address

                                      -6-
<PAGE>

                                   EXHIBIT A
                                   ---------

                                1997 STOCK PLAN

                                EXERCISE NOTICE

Numerical Technologies, Inc.
70 West Plumeria Drive
San Jose, CA  95134-2134

Attention:  Secretary

     1.   Exercise of Option.  Effective as of today, _____________, _____, the
          ------------------
undersigned ("Optionee") hereby elects to exercise Optionee's option to purchase
_________ shares of the Common Stock (the "Shares") of Numerical Technologies,
Inc. (the "Company") under and pursuant to the 1997 Stock Plan (the "Plan") and
the [  ] Incentive [  ] Nonstatutory Stock Option Agreement dated ____________,
______ (the "Option Agreement").

     2.   Delivery of Payment.  Purchaser herewith delivers to the Company the
          -------------------
full purchase price of the Shares, as set forth in the Option Agreement.

     3.   Representations of Optionee.  Optionee acknowledges that Optionee has
          ---------------------------
received, read and understood the Plan and the Option Agreement and agrees to
abide by and be bound by their terms and conditions.

     4.   Rights as Shareholder.  Until the issuance of the Shares (as
          ---------------------
evidenced by the appropriate entry on the books of the Company or of a duly
authorized transfer agent of the Company), no right to vote or receive dividends
or any other rights as a shareholder shall exist with respect to the Optioned
Stock, notwithstanding the exercise of the Option. The Shares shall be issued to
the Optionee as soon as practicable after the Option is exercised. No adjustment
shall be made for a dividend or other right for which the record date is prior
to the date of issuance except as provided in Section 12 of the Plan.

     5.   Company's Right of First Refusal.  Before any Shares held by
          --------------------------------
Optionee or any transferee (either being sometimes referred to herein as the
"Holder") may be sold or otherwise transferred (including transfer by gift or
operation of law), the Company or its assignee(s) shall have a right of first
refusal to purchase the Shares on the terms and conditions set forth in this
Section (the "Right of First Refusal").

          (a)  Notice of Proposed Transfer.  The Holder of the Shares shall
               ---------------------------
deliver to the Company a written notice (the "Notice") stating: (i) the Holder's
bona fide intention to sell or otherwise transfer such Shares; (ii) the name of
each proposed purchaser or other transferee ("Proposed Transferee"); (iii) the
number of Shares to be transferred to each Proposed Transferee; and (iv) the
bona fide cash price or other consideration for which the Holder proposes to
transfer the
<PAGE>

Shares (the "Offered Price"), and the Holder shall offer the Shares at the
Offered Price to the Company or its assignee(s).

          (b)  Exercise of Right of First Refusal.  At any time within thirty
               ----------------------------------
(30) days after receipt of the Notice, the Company and/or its assignee(s) may,
by giving written notice to the Holder, elect to purchase all, but not less than
all, of the Shares proposed to be transferred to any one or more of the Proposed
Transferees, at the purchase price determined in accordance with subsection (c)
below.

          (c)  Purchase Price.  The purchase price ("Purchase Price") for the
               --------------
Shares purchased by the Company or its assignee(s) under this Section shall be
the Offered Price. If the Offered Price includes consideration other than cash,
the cash equivalent value of the non-cash consideration shall be determined by
the Board of Directors of the Company in good faith.

          (d)  Payment.  Payment of the Purchase Price shall be made, at the
               -------
option of the Company or its assignee(s), in cash (by check), by cancellation of
all or a portion of any outstanding indebtedness of the Holder to the Company
(or, in the case of repurchase by an assignee, to the assignee), or by any
combination thereof within 30 days after receipt of the Notice or in the manner
and at the times set forth in the Notice.

          (e)  Holder's Right to Transfer.  If all of the Shares proposed in the
               --------------------------
Notice to be transferred to a given Proposed Transferee are not purchased by the
Company and/or its assignee(s) as provided in this Section, then the Holder may
sell or otherwise transfer such Shares to that Proposed Transferee at the
Offered Price or at a higher price, provided that such sale or other transfer is
consummated within 120 days after the date of the Notice, that any such sale or
other transfer is effected in accordance with any applicable securities laws and
that the Proposed Transferee agrees in writing that the provisions of this
Section shall continue to apply to the Shares in the hands of such Proposed
Transferee.  If the Shares described in the Notice are not transferred to the
Proposed Transferee within such period, a new Notice shall be given to the
Company, and the Company and/or its assignees shall again be offered the Right
of First Refusal before any Shares held by the Holder may be sold or otherwise
transferred.

          (f)  Exception for Certain Family Transfers.  Anything to the contrary
               --------------------------------------
contained in this Section notwithstanding, the transfer of any or all of the
Shares during the Optionee's lifetime or on the Optionee's death by will or
intestacy to the Optionee's immediate family or a trust for the benefit of the
Optionee's immediate family shall be exempt from the provisions of this Section.
"Immediate Family" as used herein shall mean spouse, lineal descendant or
antecedent, father, mother, brother or sister.  In such case, the transferee or
other recipient shall receive and hold the Shares so transferred subject to the
provisions of this Section, and there shall be no further transfer of such
Shares except in accordance with the terms of this Section.

          (g)  Termination of Right of First Refusal.  The Right of First
               -------------------------------------
Refusal shall terminate as to any Shares upon the first sale of Common Stock of
the Company to the general public pursuant to a registration statement filed
with and declared effective by the Securities and Exchange Commission under the
Securities Act of 1933, as amended.

                                      -2-
<PAGE>

     6.   Tax Consultation.  Optionee understands that Optionee may suffer
          ----------------
adverse tax consequences as a result of Optionee's purchase or disposition of
the Shares. Optionee represents that Optionee has consulted with any tax
consultants Optionee deems advisable in connection with the purchase or
disposition of the Shares and that Optionee is not relying on the Company for
any tax advice.

     7.   Restrictive Legends and Stop-Transfer Orders.
          --------------------------------------------

          (a)  Legends.  Optionee understands and agrees that the Company shall
               -------
cause the legends set forth below or legends substantially equivalent thereto,
to be placed upon any certificate(s) evidencing ownership of the Shares together
with any other legends that may be required by the Company or by state or
federal securities laws:

          THE SECURITIES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE
          SECURITIES ACT OF 1933 (THE "ACT") AND MAY NOT BE OFFERED, SOLD OR
          OTHERWISE TRANSFERRED, PLEDGED OR HYPOTHECATED UNLESS AND UNTIL
          REGISTERED UNDER THE ACT OR, IN THE OPINION OF COMPANY COUNSEL
          SATISFACTORY TO THE ISSUER OF THESE SECURITIES, SUCH OFFER, SALE OR
          TRANSFER, PLEDGE OR HYPOTHECATION IS IN COMPLIANCE THEREWITH.

          THE SHARES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO CERTAIN
          RESTRICTIONS ON TRANSFER AND RIGHT OF FIRST REFUSAL OPTIONS HELD BY
          THE ISSUER OR ITS ASSIGNEE(S) AS SET FORTH IN THE EXERCISE NOTICE
          BETWEEN THE ISSUER AND THE ORIGINAL HOLDER OF THESE SHARES, A COPY OF
          WHICH MAY BE OBTAINED AT THE PRINCIPAL OFFICE OF THE ISSUER.  SUCH
          TRANSFER RESTRICTIONS AND RIGHT OF FIRST REFUSAL ARE BINDING ON
          TRANSFEREES OF THESE SHARES.

          (b)  Stop-Transfer Notices.  Optionee agrees that, in order to ensure
               ---------------------
compliance with the restrictions referred to herein, the Company may issue
appropriate "stop transfer" instructions to its transfer agent, if any, and
that, if the Company  transfers its own securities, it may make appropriate
notations to the same effect in its own records.

          (c)  Refusal to Transfer.  The Company shall not be required (i) to
               -------------------
transfer on its books any Shares that have been sold or otherwise transferred in
violation of any of the provisions of this Agreement or (ii) to treat as owner
of such Shares or to accord the right to vote or pay dividends to any purchaser
or other transferee to whom such Shares shall have been so transferred.

     8.   Successors and Assigns.  The Company may assign any of its rights
          ----------------------
under this Agreement to single or multiple assignees, and this Agreement shall
inure to the benefit of the successors and assigns of the Company. Subject to
the restrictions on transfer herein set forth, this Agreement shall be binding
upon Optionee and his or her heirs, executors, administrators, successors and
assigns.

                                      -3-
<PAGE>

     9.   Interpretation.  Any dispute regarding the interpretation of this
          --------------
Agreement shall be submitted by Optionee or by the Company forthwith to the
Administrator which shall review such dispute at its next regular meeting.  The
resolution of such a dispute by the Administrator shall be final and binding on
all parties.

     10.  Governing Law; Severability.  This Agreement is governed by the
          ---------------------------
internal substantive laws, but not the choice of law rules, of California.

     11.  Entire Agreement.  The Plan and Option Agreement are incorporated
          ----------------
herein by reference.  This Agreement, the Plan, the Restricted Stock Purchase
Agreement, the Option Agreement and the Investment Representation Statement
constitute the entire agreement of the parties with respect to the subject
matter hereof and supersede in their entirety all prior undertakings and
agreements of the Company and Optionee with respect to the subject matter
hereof, and may not be modified adversely to the Optionee's interest except by
means of a writing signed by the Company and Optionee.

Submitted by:                           Accepted by:

OPTIONEE:                               NUMERICAL TECHNOLOGIES, INC.

________________________________        ________________________________
Signature                               By

________________________________        ________________________________
Print Name                              Its

Address:                                Address:
-------                                 -------

--------------------------------        70 West Plumeria Drive
                                        San Jose, CA  95134-2134

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

                                        ________________________________
                                        Date Received

                                      -4-
<PAGE>

                                   EXHIBIT B
                                   ---------

                      INVESTMENT REPRESENTATION STATEMENT

OPTIONEE       :

COMPANY        :    NUMERICAL TECHNOLOGIES, INC.

SECURITY       :    COMMON STOCK

AMOUNT         :

DATE           :

     In connection with the purchase of the above-listed Securities, the
undersigned Optionee represents to the Company the following:

          (a)  Optionee is aware of the Company's business affairs and financial
condition and has acquired sufficient information about the Company to reach an
informed and knowledgeable decision to acquire the Securities.  Optionee is
acquiring these Securities for investment for Optionee's own account only and
not with a view to, or for resale in connection with, any "distribution" thereof
within the meaning of the Securities Act of 1933, as amended (the "Securities
Act").

          (b)  Optionee acknowledges and understands that the Securities
constitute "restricted securities" under the Securities Act and have not been
registered under the Securities Act in reliance upon a specific exemption
therefrom, which exemption depends upon, among other things, the bona fide
nature of Optionee's investment intent as expressed herein. In this connection,
Optionee understands that, in the view of the Securities and Exchange
Commission, the statutory basis for such exemption may be unavailable if
Optionee's representation was predicated solely upon a present intention to hold
these Securities for the minimum capital gains period specified under tax
statutes, for a deferred sale, for or until an increase or decrease in the
market price of the Securities, or for a period of one year or any other fixed
period in the future. Optionee further understands that the Securities must be
held indefinitely unless they are subsequently registered under the Securities
Act or an exemption from such registration is available. Optionee further
acknowledges and understands that the Company is under no obligation to register
the Securities. Optionee understands that the certificate evidencing the
Securities will be imprinted with a legend which prohibits the transfer of the
Securities unless they are registered or such registration is not required in
the opinion of counsel satisfactory to the Company, and any other legend
required under applicable state securities laws.

          (c)  Optionee is familiar with the provisions of Rule 701 and Rule
144, each promulgated under the Securities Act, which, in substance, permit
limited public resale of "restricted securities" acquired, directly or
indirectly from the issuer thereof, in a non-public offering subject to
<PAGE>

the satisfaction of certain conditions. Rule 701 provides that if the issuer
qualifies under Rule 701 at the time of the grant of the Option to the Optionee,
the exercise will be exempt from registration under the Securities Act. In the
event the Company becomes subject to the reporting requirements of Section 13 or
15(d) of the Securities Exchange Act of 1934, ninety (90) days thereafter (or
such longer period as any market stand-off agreement may require) the Securities
exempt under Rule 701 may be resold, subject to the satisfaction of certain of
the conditions specified by Rule 144, including: (1) the resale being made
through a broker in an unsolicited "broker's transaction" or in transactions
directly with a market maker (as said term is defined under the Securities
Exchange Act of 1934); and, in the case of an affiliate, (2) the availability of
certain public information about the Company, (3) the amount of Securities being
sold during any three month period not exceeding the limitations specified in
Rule 144(e), and (4) the timely filing of a Form 144, if applicable.

     In the event that the Company does not qualify under Rule 701 at the time
of grant of the Option, then the Securities may be resold in certain limited
circumstances subject to the provisions of Rule 144, which requires the resale
to occur not less than one year after the later of the date the Securities were
sold by the Company or the date the Securities were sold by an affiliate of the
Company, within the meaning of Rule 144; and, in the case of acquisition of the
Securities by an affiliate, or by a non-affiliate who subsequently holds the
Securities less than two years, the satisfaction of the conditions set forth in
sections (1), (2), (3) and (4) of the paragraph immediately above.

          (d)  Optionee further understands that in the event all of the
applicable requirements of Rule 701 or 144 are not satisfied, registration under
the Securities Act, compliance with Regulation A, or some other registration
exemption will be required; and that, notwithstanding the fact that Rules 144
and 701 are not exclusive, the Staff of the Securities and Exchange Commission
has expressed its opinion that persons proposing to sell private placement
securities other than in a registered offering and otherwise than pursuant to
Rules 144 or 701 will have a substantial burden of proof in establishing that an
exemption from registration is available for such offers or sales, and that such
persons and their respective brokers who participate in such transactions do so
at their own risk. Optionee understands that no assurances can be given that any
such other registration exemption will be available in such event.

                                             Signature of Optionee:

                                             ___________________________________

                                             Date:______________________, ______

                                      -2-
<PAGE>

                                  EXHIBIT C-1
                                  -----------

                         NUMERICAL TECHNOLOGIES, INC.

                                1997 STOCK PLAN

                      RESTRICTED STOCK PURCHASE AGREEMENT

     THIS AGREEMENT is made between ____________________________________ (the
"Purchaser") and Numerical Technologies, Inc. (the "Company") as of
__________________, _____.

                                   RECITALS
                                   --------

     (1) Pursuant to the exercise of the stock option granted to Purchaser under
the Company's 1997 Stock Plan (the "Plan") and pursuant to the Stock Option
Agreement (the "Option Agreement") dated ____________, _____ by and between the
Company and Purchaser with respect to such grant, which Plan and Option
Agreement are hereby incorporated by reference, Purchaser has elected to
purchase _________ of those shares which have not become vested under the
vesting schedule set forth in the Option Agreement ("Unvested Shares").  The
Unvested Shares and the shares subject to the Option Agreement which have become
vested are sometimes collectively referred to herein as the "Shares".

     (2) As required by the Option Agreement, as a condition to Purchaser's
election to exercise the option, Purchaser must execute this Restricted Stock
Purchase Agreement, which sets forth the rights and obligations of the parties
with respect to Shares acquired upon exercise of the Option.

     1.  Repurchase Option.
         -----------------

         (a)  If Purchaser's status as a Service Provider is terminated for any
reason, including for cause, death, and disability, the Company shall have the
right and option to purchase from Purchaser, or Purchaser's personal
representative, as the case may be, all of the Purchaser's Unvested Shares as of
the date of such termination at the price paid by the Purchaser for such Shares
(the "Repurchase Option").

         (b)  Upon the occurrence of a termination, the Company may exercise its
Repurchase Option by delivering personally or by registered mail, to Purchaser
(or his transferee or legal representative, as the case may be), within ninety
(90) days of the termination, a notice in writing indicating the Company's
intention to exercise the Repurchase Option and setting forth a date for closing
not later than thirty (30) days from the mailing of such notice. The closing
shall take place at the Company's office. At the closing, the holder of the
certificates for the Unvested Shares being transferred shall deliver the stock
certificate or certificates evidencing the Unvested Shares, and the Company
shall deliver the purchase price therefor.
<PAGE>

          (c)  At its option, the Company may elect to make payment for the
Unvested Shares to a bank selected by the Company. The Company shall avail
itself of this option by a notice in writing to Purchaser stating the name and
address of the bank, date of closing, and waiving the closing at the Company's
office.

          (d)  If the Company does not elect to exercise the Repurchase Option
conferred above by giving the requisite notice within ninety (90) days following
the termination, the Repurchase Option shall terminate.

          (e)  The Repurchase Option shall terminate in accordance with the
Vesting Schedule in Optionee's Option Agreement.

     2.   Transferability of the Shares; Escrow.
          -------------------------------------

          (a)  Purchaser hereby authorizes and directs the secretary of the
Company, or such other person designated by the Company, to transfer the
Unvested Shares as to which the Repurchase Option has been exercised from
Purchaser to the Company.

          (b)  To insure the availability for delivery of Purchaser's Unvested
Shares upon repurchasby the Company pursuant to the Repurchase Option under
Section 1, Purchaser hereby appoints the secretary, or any other person
designated by the Company as escrow agent, as its attorney-in-fact to sell,
assign and transfer unto the Company, such Unvested Shares, if any, repurchased
by the Company pursuant to the Repurchase Option and shall, upon execution of
this Agreement, deliver and deposit with the secretary of the Company, or such
other person designated by the Company, the share certificates representing the
Unvested Shares, together with the stock assignment duly endorsed in blank,
attached hereto as Exhibit C-2. The Unvested Shares and stock assignment shall
                   -----------
be held by the secretary in escrow, pursuant to the Joint Escrow Instructions of
the Company and Purchaser attached as Exhibit C-3 hereto, until the Company
                                      -----------
exercises its purchase right as provided in Section 1, until such Unvested
Shares are vested, or until such time as this Agreement no longer is in effect.
As a further condition to the Company's obligations under this Agreement, the
spouse of the Purchaser, if any, shall execute and deliver to the Company the
Consent of Spouse attached hereto as Exhibit C-4. Upon vesting of the Unvested
                                     -----------
Shares, the escrow agent shall promptly deliver to the Purchaser the certificate
or certificates representing such Shares in the escrow agent's possession
belonging to the Purchaser, and the escrow agent shall be discharged of all
further obligations hereunder; provided, however, that the escrow agent shall
nevertheless retain such certificate or certificates as escrow agent if so
required pursuant to other restrictions imposed pursuant to this Agreement.

          (c)  The Company, or its designee, shall not be liable for any act it
may do or omit to do with respect to holding the Shares in escrow and while
acting in good faith and in the exercise of its judgment.

          (d)  Transfer or sale of the Shares is subject to restrictions on
transfer imposed by any applicable state and federal securities laws. Any
transferee shall hold such Shares subject to all the provisions hereof and the
Exercise Notice executed by the Purchaser with respect to any

                                      -2-
<PAGE>

Unvested Shares purchased by Purchaser and shall acknowledge the same by signing
a copy of this Agreement.

     3.   Ownership, Voting Rights, Duties. This Agreement shall not affect in
          --------------------------------
any way the ownership, voting rights or other rights or duties of Purchaser,
except as specifically provided herein.

     4.   Legends.  The share certificate evidencing the Shares issued hereunder
          -------
shall be endorsed with the following legend (in addition to any legend required
under applicable state securities laws):

     THE SHARES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO CERTAIN
RESTRICTIONS UPON TRANSFER AND RIGHTS OF REPURCHASE AS SET FORTH IN AN AGREEMENT
BETWEEN THE COMPANY AND THE STOCKHOLDER, A COPY OF WHICH IS ON FILE WITH THE
SECRETARY OF THE COMPANY.

     5.   Adjustment for Stock Split. All references to the number of Shares and
          --------------------------
the purchase price of the Shares in this Agreement shall be appropriately
adjusted to reflect any stock split, stock dividend or other change in the
Shares which may be made by the Company after the date of this Agreement.

     6.   Notices.  Notices required hereunder shall be given in person or by
          -------
registered mail to the address of Purchaser shown on the records of the Company,
and to the Company at their respective principal executive offices.

     7.   Survival of Terms. This Agreement shall apply to and bind Purchaser
          -----------------
and the Company and their respective permitted assignees and transferees, heirs,
legatees, executors, administrators and legal successors.

     8.   Section 83(b) Election.  Purchaser hereby acknowledges that he or she
          ----------------------
has been informed that, with respect to the exercise of an Option for unvested
Shares, an election may be filed by the Purchaser with the Internal Revenue
Service, within 30 days of the purchase of the Shares, electing pursuant to
         --------------
Section 83(b) of the Code to be taxed currently on any difference between the
purchase price of the Shares and their Fair Market Value on the date of
purchase. In the case of a Nonstatutory Stock Option, this will result in a
recognition of taxable income to the Purchaser on the date of exercise, measured
by the excess, if any, of the fair market value of the Shares, at the time the
Option is exercised over the purchase price for the Shares. Absent such an
election, taxable income will be measured and recognized by Purchaser at the
time or times on which the Company's Repurchase Option lapses. In the case of an
Incentive Stock Option, such an election will result in a recognition of income
to the Purchaser for alternative minimum tax purposes on the date of exercise,
measured by the excess, if any, of the fair market value of the Shares, at the
time the option is exercised, over the purchase price for the Shares. Absent
such an election, alternative minimum taxable income will be measured and
recognized by Purchaser at the time or times on which the Company's Repurchase
Option lapses. Purchaser is strongly encouraged to seek the advice of his or her
own tax consultants in connection with the purchase of the Shares and the
advisability of filing

                                      -3-
<PAGE>

of the Election under Section 83(b) of the Code. A form of Election under
Section 83(b) is attached hereto as Exhibit C-5 for reference.
                                    -----------

     PURCHASER ACKNOWLEDGES THAT IT IS PURCHASER'S SOLE RESPONSIBILITY AND NOT
THE COMPANY'S TO FILE TIMELY THE ELECTION UNDER SECTION 83(b), EVEN IF PURCHASER
REQUESTS THE COMPANY OR ITS REPRESENTATIVE TO MAKE THIS FILING ON PURCHASER'S
BEHALF.

     9.   Representations.  Purchaser has reviewed with his own tax advisors the
          ---------------
federal, state, local and foreign tax consequences of this investment and the
transactions contemplated by this Agreement. Purchaser is relying solely on such
advisors and not on any statements or representations of the Company or any of
its agents. Purchaser understands that he (and not the Company) shall be
responsible for his own tax liability that may arise as a result of this
investment or the transactions contemplated by this Agreement.

     10.  Governing Law.  This Agreement shall be governed by the internal
          -------------
substantive laws, but not the choice of law rules, of California.

     Purchaser represents that he has read this Agreement and is familiar with
its terms and provisions.  Purchaser hereby agrees to accept as binding,
conclusive and final all decisions or interpretations of the Board upon any
questions arising under this Agreement.

                                      -4-
<PAGE>

     IN WITNESS WHEREOF, this Agreement is deemed made as of the date first set
forth above.

                                    "COMPANY"

                                    NUMERICAL TECHNOLOGIES, INC

                                    _______________________________________
                                    By

                                    _______________________________________
                                    Title

                                    "PURCHASER"

                                    _______________________________________
                                    Signature

                                    _______________________________________
                                    Printed Name

                                    _______________________________________
                                    Soc. Sec. No.

                                    Address:
                                    -------

                                    _______________________________________

                                    _______________________________________

                                      -5-
<PAGE>

                                  EXHIBIT C-2
                                  -----------

                     ASSIGNMENT SEPARATE FROM CERTIFICATE

     FOR VALUE RECEIVED I, __________________________, hereby sell, assign and
transfer unto Numerical Technologies, Inc. (__________) shares of the Common
Stock of Numerical Technologies, Inc. standing in my name of the books of said
corporation represented by Certificate No. _____ herewith and do hereby
irrevocably constitute and appoint    to transfer the said stock on the books of
the within named corporation with full power of substitution in the premises.

     This Stock Assignment may be used only in accordance with the Restricted
Stock Purchase Agreement between Numerical Technologies, Inc. and the
undersigned dated ______________, _____.

Dated: _______________, ______

       Signature:________________________________

INSTRUCTIONS: Please do not fill in any blanks other than the signature line.
The purpose of this assignment is to enable the Company to exercise its
"repurchase option," as set forth in the Agreement, without requiring additional
signatures on the part of the Purchaser.
<PAGE>

                                  EXHIBIT C-3
                                  -----------

                           JOINT ESCROW INSTRUCTIONS

                                                             ____________, _____

Numerical Technologies, Inc.
70 West Plumeria Drive
San Jose, CA  95134-2134
Attention:  Secretary

Dear:

     As Escrow Agent for both Numerical Technologies, Inc. (the "Company"), and
the undersigned purchaser of stock of the Company (the "Purchaser"), you are
hereby authorized and directed to hold the documents delivered to you pursuant
to the terms of that certain Restricted Stock Purchase Agreement ("Agreement")
between the Company and the undersigned, in accordance with the following
instructions:

     1.   In the event the Company and/or any assignee of the Company (referred
to collectively for convenience herein as the "Company") exercises the Company's
repurchase option set forth in the Agreement, the Company shall give to
Purchaser and you a written notice specifying the number of shares of stock to
be purchased, the purchase price, and the time for a closing hereunder at the
principal office of the Company. Purchaser and the Company hereby irrevocably
authorize and direct you to close the transaction contemplated by such notice in
accordance with the terms of said notice.

     2.   At the closing, you are directed (a) to date the stock assignments
necessary for the transfer in question, (b) to fill in the number of shares
being transferred, and (c) to deliver same, together with the certificate
evidencing the shares of stock to be transferred, to the Company or its
assignee, against the simultaneous delivery to you of the purchase price (by
cash, a check, or some combination thereof) for the number of shares of stock
being purchased pursuant to the exercise of the Company's repurchase option.

     3.   Purchaser irrevocably authorizes the Company to deposit with you any
certificates evidencing shares of stock to be held by you hereunder and any
additions and substitutions to said shares as defined in the Agreement.
Purchaser does hereby irrevocably constitute and appoint you as Purchaser's
attorney-in-fact and agent for the term of this escrow to execute with respect
to such securities all documents necessary or appropriate to make such
securities negotiable and to complete any transaction herein contemplated,
including but not limited to the filing with any applicable state blue sky
authority of any required applications for consent to, or notice of transfer of,
the securities. Subject to the provisions of this paragraph 3, Purchaser shall
exercise all rights and privileges of a stockholder of the Company while the
stock is held by you.
<PAGE>

     4.   Upon written request of the Purchaser, but no more than once per
calendar year, unless the Company's repurchase option has been exercised, you
will deliver to Purchaser a certificate or certificates representing so many
shares of stock as are not then subject to the Company's repurchase option.
Within 120 days after cessation of Purchaser's continuous employment by or
services to the Company, or any parent or subsidiary of the Company, you will
deliver to Purchaser a certificate or certificates representing the aggregate
number of shares held or issued pursuant to the Agreement and not purchased by
the Company or its assignees pursuant to exercise of the Company's repurchase
option.

     5.   If at the time of termination of this escrow you should have in your
possession any documents, securities, or other property belonging to Purchaser,
you shall deliver all of the same to Purchaser and shall be discharged of all
further obligations hereunder.

     6.   Your duties hereunder may be altered, amended, modified or revoked
only by a writing signed by all of the parties hereto.

     7.   You shall be obligated only for the performance of such duties as are
specifically set forth herein and may rely and shall be protected in relying or
refraining from acting on any instrument reasonably believed by you to be
genuine and to have been signed or presented by the proper party or parties. You
shall not be personally liable for any act you may do or omit to do hereunder as
Escrow Agent or as attorney-in-fact for Purchaser while acting in good faith,
and any act done or omitted by you pursuant to the advice of your own attorneys
shall be conclusive evidence of such good faith.

     8.   You are hereby expressly authorized to disregard any and all warnings
given by any of the parties hereto or by any other person or corporation,
excepting only orders or process of courts of law and are hereby expressly
authorized to comply with and obey orders, judgments or decrees of any court. In
case you obey or comply with any such order, judgment or decree, you shall not
be liable to any of the parties hereto or to any other person, firm or
corporation by reason of such compliance, notwithstanding any such order,
judgment or decree being subsequently reversed, modified, annulled, set aside,
vacated or found to have been entered without jurisdiction.

     9.   You shall not be liable in any respect on account of the identity,
authorities or rights of the parties executing or delivering or purporting to
execute or deliver the Agreement or any documents or papers deposited or called
for hereunder.

     10.  You shall not be liable for the outlawing of any rights under the
Statute of Limitations with respect to these Joint Escrow Instructions or any
documents deposited with you.

     11.  You shall be entitled to employ such legal counsel and other experts
as you may deem necessary properly to advise you in connection with your
obligations hereunder, may rely upon the advice of such counsel, and may pay
such counsel reasonable compensation therefor.

                                      -2-
<PAGE>

     12.  Your responsibilities as Escrow Agent hereunder shall terminate if you
shall cease to be an officer or agent of the Company or if you shall resign by
written notice to each party. In the event of any such termination, the Company
shall appoint a successor Escrow Agent.

     13.  If you reasonably require other or further instruments in connection
with these Joint Escrow Instructions or obligations in respect hereto, the
necessary parties hereto shall join in furnishing such instruments.

     14.  It is understood and agreed that should any dispute arise with respect
to the delivery and/or ownership or right of possession of the securities held
by you hereunder, you are authorized and directed to retain in your possession
without liability to anyone all or any part of said securities until such
disputes shall have been settled either by mutual written agreement of the
parties concerned or by a final order, decree or judgment of a court of
competent jurisdiction after the time for appeal has expired and no appeal has
been perfected, but you shall be under no duty whatsoever to institute or defend
any such proceedings.

     15.  Any notice required or permitted hereunder shall be given in writing
and shall be deemed effectively given upon personal delivery or upon deposit in
the United States Post Office, by registered or certified mail with postage and
fees prepaid, addressed to each of the other parties thereunto entitled at the
following addresses or at such other addresses as a party may designate by ten
days' advance written notice to each of the other parties hereto.

          COMPANY:       Numerical Technologies, Inc.
                         70 West Plumeria Drive
                         San Jose, CA 95134-2134
                         Attention:  Secretary

          PURCHASER:     ____________________________

          ESCROW AGENT:  Wilson Sonsini Goodrich & Rosati
                         650 Page Mill Road
                         Palo Alto, CA 94304

     16.  By signing these Joint Escrow Instructions, you become a party hereto
only for the purpose of said Joint Escrow Instructions; you do not become a
party to the Agreement.

     17.  This instrument shall be binding upon and inure to the benefit of the
parties hereto, and their respective successors and permitted assigns.

                                      -3-
<PAGE>

     18.  These Joint Escrow Instructions shall be governed by the internal
substantive laws, but not the choice of law rules, of California.

                                    NUMERICAL TECHNOLOGIES, INC.

                                    ______________________________
                                    By

                                    ______________________________
                                    Title

                                    PURCHASER

                                    ______________________________
                                    Signature

                                    ______________________________
                                    Typed or Printed Name

                                    ESCROW AGENT

                                    WILSON SONSINI GOODRICH & ROSATI

                                    ______________________________
                                    By

                                    ______________________________
                                    Title

                                      -4-
<PAGE>

                                 EXHIBIT  C-4
                                 ------------

                               CONSENT OF SPOUSE
                               -----------------

     I, ____________________, spouse of ___________________, have read and
approve the foregoing Agreement.  In consideration of granting of the right to
my spouse to purchase shares of ____________________________, as set forth in
the Agreement, I hereby appoint my spouse as my attorney-in-fact in respect to
the exercise of any rights under the Agreement and agree to be bound by the
provisions of the Agreement insofar as I may have any rights in said Agreement
or any shares issued pursuant thereto under the community property laws or
similar laws relating to marital property in effect in the state of our
residence as of the date of the signing of the foregoing Agreement.

Dated: _______________,  _____

                                             ______________________________

<PAGE>

                                  EXHIBIT C-5
                                  -----------

                         ELECTION UNDER SECTION 83(b)
                         -----------------------------
                     OF THE INTERNAL REVENUE CODE OF 1986
                     ------------------------------------

The undersigned taxpayer hereby elects, pursuant to Sections 55 and 83(b) of the
Internal Revenue Code of 1986, as amended, to include in taxpayer's gross income
or alternative minimum taxable income, as the case may be, for the current
taxable year the amount of any compensation taxable to taxpayer in connection
with taxpayer's receipt of the property described below:

1.   The name, address, taxpayer identification number and taxable year of the
undersigned are as follows:

     NAME:                 TAXPAYER:                SPOUSE:

     ADDRESS:

     IDENTIFICATION NO.:   TAXPAYER:                SPOUSE:

     TAXABLE YEAR:

2.   The property with respect to which the election is made is described as
follows:______________________________ shares (the "Shares") of the Common Stock
of ___________________________ (the "Company").

3.   The date on which the property was transferred is:  _______________, _____.

4.   The property is subject to the following restrictions:

     The Shares may not be transferred and are subject to forfeiture under the
terms of an agreement between the taxpayer and the Company.  These restrictions
lapse upon the satisfaction of certain conditions contained in such agreement.

5.   The fair market value at the time of transfer, determined without regard to
any restriction other than a restriction which by its terms will never lapse, of
such property is:
     $______________________.

6.   The amount (if any) paid for such property is:
     $______________________.

The undersigned has submitted a copy of this statement to the person for whom
the services were performed in connection with the undersigned's receipt of the
above-described property.  The transferee of such property is the person
performing the services in connection with the transfer of said property.

The undersigned understands that the foregoing election may not be revoked
--------------------------------------------------------------------------
except with the consent of the Commissioner.
-------------------------------------------

Dated:  ___________________, _____           ___________________________________
                                             Taxpayer

The undersigned spouse of taxpayer joins in this election.

Dated:  ___________________, _____           ___________________________________<PAGE>
                                                                  Exhibit 10.28
                         NUMERICAL TECHNOLOGIES, INC.

                                2000 STOCK PLAN

                   STOCK OPTION AGREEMENT -- EARLY EXERCISE

     Unless otherwise defined herein, the terms defined in the Plan shall have
the same defined meanings in this Option Agreement.

I.   NOTICE OF STOCK OPTION GRANT
     ----------------------------

     Roger Sturgeon

     You have been granted an option to purchase Common Stock of the Company,
subject to the terms and conditions of the Plan and this Option Agreement, as
follows:

     Date of Grant:                          February 1, 2000

     Vesting Commencement Date:              January 1, 2000

     Exercise Price per Share:               $4.00

     Total Number of Shares Granted:         150,000

     Total Exercise Price:                   $600,000.00

     Type of Option:                         ___ Incentive Stock Option

                                              X  Nonstatutory Stock Option
                                             ---

     Term/Expiration Date:                   Ten Years/February 1,2010*

________________
* Or earlier, pursuant to the termination period set forth below.

     Exercise and Vesting Schedule:
     -----------------------------

     This Option is exercisable immediately, in whole or in part, and shall vest
according to the following vesting schedule:

     One-half (1/2) of the Shares subject to this Option shall vest on January
1, 2002 and one-sixteenth (1/16th) of the Shares subject to this Option shall
vest on April 1, 2002 and on the last day of each three month anniversary
thereafter, subject to your continuing to be a Service Provider on such dates;
provided, however, if your employment with the Company is terminated prior to
January 1, 2002 by reason of your death or disability (as defined in the Plan),
then the shares shall
<PAGE>

become vested on an accelerated basis, and the Company's repurchase right shall
accordingly lapse, in accordance with the following schedule: one-sixteenth
(1/16th) of the shares subject to this Option shall vest for each three (3)
month period, measured from January 1, 2000, for which you completed employment
with the Company prior to your termination by reason of death or disability.

     Change of Control; Constructive Termination:
     -------------------------------------------

     Notwithstanding the provisions of Section 14(c) of the Plan, if the Company
merges with or into another entity, sells all or substantially all of its
assets, or enters into any other similar transaction or reorganization
(including without limitation, a sale of stock of the Company) as a result of
which the shareholders of the Company immediately prior to such transaction will
not hold at least 50% of the voting power of the surviving, purchasing or
continuing entity, as applicable (taking into account any securities issued to
the shareholders of the Company in the transaction) (a "Change of Control
Transaction"), then on the later of (i) January 2, 2002 (the "Two Year
Employment Anniversary Date") or (ii) the six month anniversary of the Change of
Control Transaction (the "Merger Anniversary Date") fifty percent (50%) of the
Shares subject to the Option which have not vested as of the Two Year Employment
Anniversary Date or the Merger Anniversary Date, as applicable, shall become
fully vested and exercisable.  The Board shall notify the Optionee at least
fifteen (15) days prior to the closing of a Change of Control Transaction, and
such notification shall include a statement as to whether or not the Option will
be assumed by the surviving or purchasing entity or whether an equivalent
substitute option will be provided by such entity.

     Following an assumption or substitution of the Option in connection with a
Change of Control Transaction, if the Optionee's status as an Employee of the
successor corporation is terminated by the successor corporation as a result of
an Involuntary Termination (as defined below) within twelve months following the
Change of Control Transaction, the Optionee shall fully vest in and have the
right to exercise the Option as to all of the Shares, including Shares as to
which the Option would not otherwise be vested or exercisable.

     Any of the following events shall constitute an "Involuntary Termination":
(i) without the Optionee's express written consent, a significant reduction of
the Optionee's duties, authority and responsibilities, relative to the
Optionee's duties, authority and responsibilities as in effect immediately prior
to the Change of Control Transaction; (ii) a material reduction in the base
salary of the Optionee as in effect immediately prior to the Change of Control
Transaction; (iii) a material reduction in the kind or level of employee
benefits, including bonuses, to which the Optionee was entitled immediately
prior to the Change of Control Transaction with the result that the Optionee's
overall benefits package is significantly reduced; (iv) the relocation of the
Optionee to a facility or a location more than sixty (60) miles from the
Optionee's then present location, without the Optionee's express written
consent; (v) any purported termination of the Optionee which is not effected for
Disability or for Cause (as defined below), or any purported termination for
which the grounds relied upon are not valid; (vi) or any act or set of facts or
circumstances which would, under California case law or statute, constitute a
constructive termination of the Optionee.

                                      -2-
<PAGE>

     "Cause" shall mean (i) any act of personal dishonesty taken by the Optionee
in connection with his responsibilities as a Service Provider and intended to
result in substantial personal enrichment of the Optionee, (ii) Optionee's
conviction of a felony, (iii) a willful act by the Optionee which constitutes
gross misconduct and which is injurious to the Successor Corporation, and (iv)
following delivery to the Optionee of a written demand for performance from the
Successor Corporation which describes the basis for the Successor Corporation's
belief that the Optionee has not substantially performed his duties, continued
violations by the Optionee of the Optionee's obligations to the Successor
Corporation which are demonstrably willful and deliberate on the Optionee's
part.

     Termination Period:
     ------------------

     You may exercise this Option for thirty days after you cease to be a
Service Provider.  Upon your death or disability, this Option may be exercised
for one year after you cease to be a Service Provider.  In no event may you
exercise this Option after the Term/Expiration Date as provided above.

II.  AGREEMENT
     ---------

     1.   Grant of Option.  The Plan Administrator of the Company hereby
          ---------------
grants to the Optionee named in the Notice of Grant (the "Optionee"), an option
(the "Option") to purchase the number of Shares set forth in the Notice of
Grant, at the exercise price per Share set forth in the Notice of Grant (the
"Exercise Price"), and subject to the terms and conditions of the Plan, which is
incorporated herein by reference. Subject to Section 17(c) of the Plan, in the
event of a conflict between the terms and conditions of the Plan and this Option
Agreement, the terms and conditions of the Plan shall prevail.

     If designated in the Notice of Grant as an Incentive Stock Option ("ISO"),
this Option is intended to qualify as an Incentive Stock Option as defined in
Section 422 of the Code.  Nevertheless, to the extent that it exceeds the
$100,000 rule of Code Section 422(d), this Option shall be treated as a
Nonstatutory Stock Option ("NSO").

     2.   Exercise of Option.  This Option shall be exercisable during its term
          ------------------
in accordance with the provisions of Section 10 of the Plan as follows:

          (a)  Right to Exercise.
               -----------------

               (i)  Subject to subsections 2(a)(ii) and 2(a)(iii) below, this
Option shall be exercisable cumulatively according to the vesting schedule set
forth in the Notice of Grant. Alternatively, at the election of the Optionee,
this option may be exercised in whole or in part at any time as to Shares which
have not yet vested. For purposes of this Stock Option Agreement, Shares subject
to the Option shall vest based on continued employment of Optionee with the
Company. Vested Shares shall not be subject to the Company's repurchase right
(as set forth in the Restricted Stock Purchase Agreement, attached hereto as
Exhibit C-1).
-----------

                                      -3-

<PAGE>

               (ii)  As a condition to exercising this Option for unvested
Shares, the Optionee shall execute the Restricted Stock Purchase Agreement.

               (iii) This Option may not be exercised for a fraction of a Share.

          (b)  Method of Exercise.  This Option shall be exercisable by
               ------------------
delivery of an exercise notice in the form attached as Exhibit A (the "Exercise
                                                       ---------
Notice") which shall state the election to exercise the Option, the number of
Shares with respect to which the Option is being exercised, and such other
representations and agreements as may be required by the Company. The Exercise
Notice shall be accompanied by payment of the aggregate Exercise Price as to all
Exercised Shares. This Option shall be deemed to be exercised upon receipt by
the Company of such fully executed Exercise Notice accompanied by the aggregate
Exercise Price.

     No Shares shall be issued pursuant to the exercise of an Option unless such
issuance and such exercise complies with Applicable Laws.  Assuming such
compliance, for income tax purposes the Shares shall be considered transferred
to the Optionee on the date on which the Option is exercised with respect to
such Shares.

     3.   Optionee's Representations.  In the event the Shares have not been
          --------------------------
registered under the Securities Act of 1933, as amended, at the time this Option
is exercised, the Optionee shall, if required by the Company, concurrently with
the exercise of all or any portion of this Option, deliver to the Company his or
her Investment Representation Statement in the form attached hereto as Exhibit
                                                                       -------
B.
-

     4.   Lock-Up Period.  Optionee hereby agrees that, if so requested by the
          --------------
Company or any representative of the underwriters (the "Managing Underwriter")
in connection with any registration of the offering of any securities of the
Company under the Securities Act, Optionee shall not sell or otherwise transfer
any Shares or other securities of the Company during the 180-day period (or such
other period as may be requested in writing by the Managing Underwriter and
agreed to in writing by the Company) (the "Market Standoff Period") following
the effective date of a registration statement of the Company filed under the
Securities Act. Such restriction shall apply only to the first registration
statement of the Company to become effective under the Securities Act that
includes securities to be sold on behalf of the Company to the public in an
underwritten public offering under the Securities Act. The Company may impose
stop-transfer instructions with respect to securities subject to the foregoing
restrictions until the end of such Market Standoff Period.

     5.   Method of Payment.  Payment of the aggregate Exercise Price shall be
          -----------------
by any of the following, or a combination thereof, at the election of the
Optionee:

          (a)  cash;

          (b)  check;

          (c)  consideration received by the Company under a formal cashless
exercise program adopted by the Company in connection with the Plan; or

                                      -4-
<PAGE>

          (d)  surrender of other Shares which, (i) in the case of Shares
acquired upon exercise of an option, have been owned by the Optionee for more
than six (6) months on the date of surrender, and (ii) have a Fair Market Value
on the date of surrender equal to the aggregate Exercise Price of the Exercised
Shares.

     6.   Restrictions on Exercise.  This Option may not be exercised until
          ------------------------
such time as the Plan has been approved by the shareholders of the Company, or
if the issuance of such Shares upon such exercise or the method of payment of
consideration for such shares would constitute a violation of any Applicable
Law.

     7.   Non-Transferability of Option.  This Option may not be transferred
          -----------------------------
in any manner otherwise than by will or by the laws of descent or distribution
and may be exercised during the lifetime of Optionee only by Optionee. The terms
of the Plan and this Option Agreement shall be binding upon the executors,
administrators, heirs, successors and assigns of the Optionee.

     8.   Term of Option.  This Option may be exercised only within the term
          --------------
set out in the Notice of Grant, and may be exercised during such term only in
accordance with the Plan and the terms of this Option.

     9.   Tax Consequences.  Set forth below is a brief summary as of the date
          ----------------
of this Option of some of the federal tax consequences of exercise of this
Option and disposition of the Shares. THIS SUMMARY IS NECESSARILY INCOMPLETE,
AND THE TAX LAWS AND REGULATIONS ARE SUBJECT TO CHANGE. THE OPTIONEE SHOULD
CONSULT A TAX ADVISER BEFORE EXERCISING THIS OPTION OR DISPOSING OF THE SHARES.

          (a)  Exercise of ISO.  If this Option qualifies as an ISO, there will
               ---------------
be no regular federal income tax liability upon the exercise of the Option,
although the excess, if any, of the Fair Market Value of the Shares on the date
of exercise over the Exercise Price will be treated as an adjustment to the
alternative minimum tax for federal tax purposes and may subject the Optionee to
the alternative minimum tax in the year of exercise.

          (b)  Exercise of ISO Following Disability.  If the Optionee ceases to
               ------------------------------------
be an Employee as a result of a disability that is not a total and permanent
disability as defined in Section 22(e)(3) of the Code, to the extent permitted
on the date of termination, the Optionee must exercise an ISO within three
months of such termination for the ISO to be qualified as an ISO.

          (c)  Exercise of Nonstatutory Stock Option.  There may be a regular
               -------------------------------------
federal income tax liability upon the exercise of a Nonstatutory Stock Option.
The Optionee will be treated as having received compensation income (taxable at
ordinary income tax rates) equal to the excess, if any, of the Fair Market Value
of the Shares on the date of exercise over the Exercise Price. If Optionee is an
Employee or a former Employee, the Company will be required to withhold from
Optionee's compensation or collect from Optionee and pay to the applicable
taxing authorities an amount in cash equal to a percentage of this compensation
income at the time of exercise, and may refuse to honor the exercise and refuse
to deliver Shares if such withholding amounts are not delivered at the time of
exercise.

                                      -5-
<PAGE>

          (d)  Disposition of Shares. In the case of an NSO, if Shares are held
               ---------------------
for at least one year, any gain realized on disposition of the Shares will be
treated as long-term capital gain for federal income tax purposes. In the case
of an ISO, if Shares transferred pursuant to the Option are held for at least
one year after exercise and at least two years after the Date of Grant, any gain
realized on disposition of the Shares will also be treated as long-term capital
gain for federal income tax purposes. If Shares purchased under an ISO are
disposed of within one year after exercise or two years after the Date of Grant,
any gain realized on such disposition will be treated as compensation income
(taxable at ordinary income rates) to the extent of the difference between the
Exercise Price and the lesser of (i) the Fair Market Value of the Shares on the
date of exercise, or (ii) the sale price of the Shares. Any additional gain will
be taxed as capital gain, short-term depending on the period that the ISO Shares
were held.

          (e)  Notice of Disqualifying Disposition of ISO Shares.  If the
               -------------------------------------------------
Option granted to Optionee herein is an ISO, and if Optionee sells or otherwise
disposes of any of the Shares acquired pursuant to the ISO on or before the
later of (i) the date two years after the Date of Grant, or (ii) the date one
year after the date of exercise, the Optionee shall immediately notify the
Company in writing of such disposition. Optionee agrees that Optionee may be
subject to income tax withholding by the Company on the compensation income
recognized by the Optionee.

          (f)  Section 83(b) Election for Unvested Shares Purchased Pursuant to
               ----------------------------------------------------------------
Options. With respect to the exercise of an Option for unvested Shares, an
-------
election may be filed by the Optionee with the Internal Revenue Service, within
                                                                         ------
30 days of the purchase of the Shares, electing pursuant to Section 83(b) of the
-------
Code to be taxed currently on any difference between the purchase price of the
Shares and their Fair Market Value on the date of purchase. In the case of a
Nonstatutory Stock Option, this will result in a recognition of taxable income
to the Optionee on the date of exercise, measured by the excess, if any, of the
fair market value of the Shares, at the time the Option is exercised over the
purchase price for the Shares. Absent such an election, taxable income will be
measured and recognized by Optionee at the time or times on which the Company's
Repurchase Option lapses. In the case of an Incentive Stock Option, such an
election will result in a recognition of income to the Optionee for alternative
minimum tax purposes on the date of exercise, measured by the excess, if any, of
the fair market value of the Shares, at the time the option is exercised, over
the purchase price for the Shares. Absent such an election, alternative minimum
taxable income will be measured and recognized by Optionee at the time or times
on which the Company's Repurchase Option lapses. Optionee is strongly encouraged
to seek the advice of his or her own tax consultants in connection with the
purchase of the Shares and the advisability of filing of the Election under
Section 83(b) of the Code. A form of Election under Section 83(b) is attached
hereto as Exhibit C-5 for reference.
          -----------

     OPTIONEE ACKNOWLEDGES THAT IT IS OPTIONEE'S SOLE RESPONSIBILITY AND NOT THE
COMPANY'S TO FILE TIMELY THE ELECTION UNDER SECTION 83(b), EVEN IF OPTIONEE
REQUESTS THE COMPANY OR ITS REPRESENTATIVE TO MAKE THIS FILING ON OPTIONEE'S
BEHALF.

                                      -6-
<PAGE>

     10.  Entire Agreement; Governing Law.  The Plan is incorporated herein by
          -------------------------------
reference.  The Plan and this Option Agreement constitute the entire agreement
of the parties with respect to the subject matter hereof and supersede in their
entirety all prior undertakings and agreements of the Company and Optionee with
respect to the subject matter hereof, and may not be modified adversely to the
Optionee's interest except by means of a writing signed by the Company and
Optionee.  This agreement is governed by the internal substantive laws but not
the choice of law rules of California.

     11.  No Guarantee of Continued Service.  OPTIONEE ACKNOWLEDGES AND AGREES
          ---------------------------------
THAT THE VESTING OF SHARES PURSUANT TO THE VESTING SCHEDULE HEREOF IS EARNED
ONLY BY CONTINUING AS A SERVICE PROVIDER AT THE WILL OF THE COMPANY (NOT THROUGH
THE ACT OF BEING HIRED, BEING GRANTED THIS OPTION OR ACQUIRING SHARES
HEREUNDER). OPTIONEE FURTHER ACKNOWLEDGES AND AGREES THAT THIS AGREEMENT, THE
TRANSACTIONS CONTEMPLATED HEREUNDER AND THE VESTING SCHEDULE SET FORTH HEREIN DO
NOT CONSTITUTE AN EXPRESS OR IMPLIED PROMISE OF CONTINUED ENGAGEMENT AS A
SERVICE PROVIDER FOR THE VESTING PERIOD, FOR ANY PERIOD, OR AT ALL, AND SHALL
NOT INTERFERE IN ANY WAY WITH OPTIONEE'S RIGHT OR THE COMPANY'S RIGHT TO
TERMINATE OPTIONEE'S RELATIONSHIP AS A SERVICE PROVIDER AT ANY TIME, WITH OR
WITHOUT CAUSE.

     Optionee acknowledges receipt of a copy of the Plan and represents that he
or she is familiar with the terms and provisions thereof, and hereby accepts
this Option subject to all of the terms and provisions thereof.  Optionee has
reviewed the Plan and this Option in their entirety, has had an opportunity to
obtain the advice of counsel prior to executing this Option and fully
understands all provisions of the Option.  Optionee hereby agrees to accept as
binding, conclusive and final all decisions or interpretations of the
Administrator upon any questions arising under the Plan or this Option.
Optionee further agrees to notify the Company upon any change in the residence
address indicated below.

OPTIONEE:                           NUMERICAL TECHNOLOGIES, INC.

/s/ Roger Sturgeon                  /s/ Yagyensh C. Pati
________________________________    ________________________________
Signature                           By

Roger Sturgeon                      President & CEO
--------------------------------    --------------------------------
Print Name                          Title

16490 Lucky Road
--------------------------------
Los Gatos, CA  95030
--------------------------------
Residence Address

                                      -7-
<PAGE>

                                   EXHIBIT A
                                   ---------

                                2000 STOCK PLAN

                                EXERCISE NOTICE

Numerical Technologies, Inc.
70 West Plumeria Drive
San Jose, CA  95134-2134

Attention:  Secretary

     1.   Exercise of Option.  Effective as of today, February 1, 2000, the
          ------------------
undersigned ("Optionee") hereby elects to exercise Optionee's option to purchase
150,000 shares of the Common Stock (the "Shares") of Numerical Technologies,
Inc. (the "Company") under and pursuant to the 2000 Stock Plan (the "Plan") and
the [ ] Incentive [X] Nonstatutory Stock Option Agreement dated February 1, 2000
(the "Option Agreement").

     2.   Delivery of Payment.  Purchaser herewith delivers to the Company the
          -------------------
full purchase price of the Shares, as set forth in the Option Agreement.

     3.   Representations of Optionee.  Optionee acknowledges that Optionee has
          ---------------------------
received, read and understood the Plan and the Option Agreement and agrees to
abide by and be bound by their terms and conditions.

     4.   Rights as Shareholder.  Until the issuance of the Shares (as
          ---------------------
evidenced by the appropriate entry on the books of the Company or of a duly
authorized transfer agent of the Company), no right to vote or receive dividends
or any other rights as a shareholder shall exist with respect to the Optioned
Stock, notwithstanding the exercise of the Option. The Shares shall be issued to
the Optionee as soon as practicable after the Option is exercised. No adjustment
shall be made for a dividend or other right for which the record date is prior
to the date of issuance except as provided in Section 14 of the Plan.

     5.   Company's Right of First Refusal.  Before any Shares held by Optionee
          --------------------------------
or any transferee (either being sometimes referred to herein as the "Holder")
may be sold or otherwise transferred (including transfer by gift or operation of
law), the Company or its assignee(s) shall have a right of first refusal to
purchase the Shares on the terms and conditions set forth in this Section (the
"Right of First Refusal").

          (a)  Notice of Proposed Transfer.  The Holder of the Shares shall
               ---------------------------
deliver to the Company a written notice (the "Notice") stating: (i) the Holder's
bona fide intention to sell or otherwise transfer such Shares; (ii) the name of
each proposed purchaser or other transferee ("Proposed Transferee"); (iii) the
number of Shares to be transferred to each Proposed Transferee; and (iv) the
bona fide cash price or other consideration for which the Holder proposes to
transfer the
<PAGE>

Shares (the "Offered Price"), and the Holder shall offer the Shares at the
Offered Price to the Company or its assignee(s).

          (b)  Exercise of Right of First Refusal.  At any time within thirty
               ----------------------------------
(30) days after receipt of the Notice, the Company and/or its assignee(s) may,
by giving written notice to the Holder, elect to purchase all, but not less than
all, of the Shares proposed to be transferred to any one or more of the Proposed
Transferees, at the purchase price determined in accordance with subsection (c)
below.

          (c)  Purchase Price.  The purchase price ("Purchase Price") for the
               --------------
Shares purchased by the Company or its assignee(s) under this Section shall be
the Offered Price. If the Offered Price includes consideration other than cash,
the cash equivalent value of the non-cash consideration shall be determined by
the Board of Directors of the Company in good faith.

          (d)  Payment.  Payment of the Purchase Price shall be made, at the
               -------
option of the Company or its assignee(s), in cash (by check), by cancellation of
all or a portion of any outstanding indebtedness of the Holder to the Company
(or, in the case of repurchase by an assignee, to the assignee), or by any
combination thereof within 30 days after receipt of the Notice or in the manner
and at the times set forth in the Notice.

          (e)  Holder's Right to Transfer.  If all of the Shares proposed in the
               --------------------------
Notice to be transferred to a given Proposed Transferee are not purchased by the
Company and/or its assignee(s) as provided in this Section, then the Holder may
sell or otherwise transfer such Shares to that Proposed Transferee at the
Offered Price or at a higher price, provided that such sale or other transfer is
consummated within 120 days after the date of the Notice, that any such sale or
other transfer is effected in accordance with any applicable securities laws and
that the Proposed Transferee agrees in writing that the provisions of this
Section shall continue to apply to the Shares in the hands of such Proposed
Transferee.  If the Shares described in the Notice are not transferred to the
Proposed Transferee within such period, a new Notice shall be given to the
Company, and the Company and/or its assignees shall again be offered the Right
of First Refusal before any Shares held by the Holder may be sold or otherwise
transferred.

          (f)  Exception for Certain Family Transfers.  Anything to the contrary
               --------------------------------------
contained in this Section notwithstanding, the transfer of any or all of the
Shares during the Optionee's lifetime or on the Optionee's death by will or
intestacy to the Optionee's immediate family or a trust for the benefit of the
Optionee's immediate family shall be exempt from the provisions of this Section.
"Immediate Family" as used herein shall mean spouse, lineal descendant or
antecedent, father, mother, brother or sister.  In such case, the transferee or
other recipient shall receive and hold the Shares so transferred subject to the
provisions of this Section, and there shall be no further transfer of such
Shares except in accordance with the terms of this Section.

          (g)  Termination of Right of First Refusal.  The Right of First
               -------------------------------------
Refusal shall terminate as to any Shares upon the first sale of Common Stock of
the Company to the general public pursuant to a registration statement filed
with and declared effective by the Securities and Exchange Commission under the
Securities Act of 1933, as amended.

                                      -2-
<PAGE>

     6.   Tax Consultation.  Optionee understands that Optionee may suffer
          ----------------
adverse tax consequences as a result of Optionee's purchase or disposition of
the Shares. Optionee represents that Optionee has consulted with any tax
consultants Optionee deems advisable in connection with the purchase or
disposition of the Shares and that Optionee is not relying on the Company for
any tax advice.

     7.   Restrictive Legends and Stop-Transfer Orders.
          --------------------------------------------

          (a)  Legends.  Optionee understands and agrees that the Company shall
               -------
cause the legends set forth below or legends substantially equivalent thereto,
to be placed upon any certificate(s) evidencing ownership of the Shares together
with any other legends that may be required by the Company or by state or
federal securities laws:

          THE SECURITIES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE
          SECURITIES ACT OF 1933 (THE "ACT") AND MAY NOT BE OFFERED, SOLD OR
          OTHERWISE TRANSFERRED, PLEDGED OR HYPOTHECATED UNLESS AND UNTIL
          REGISTERED UNDER THE ACT OR, IN THE OPINION OF COMPANY COUNSEL
          SATISFACTORY TO THE ISSUER OF THESE SECURITIES, SUCH OFFER, SALE OR
          TRANSFER, PLEDGE OR HYPOTHECATION IS IN COMPLIANCE THEREWITH.

          THE SHARES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO CERTAIN
          RESTRICTIONS ON TRANSFER AND RIGHT OF FIRST REFUSAL OPTIONS HELD BY
          THE ISSUER OR ITS ASSIGNEE(S) AS SET FORTH IN THE EXERCISE NOTICE
          BETWEEN THE ISSUER AND THE ORIGINAL HOLDER OF THESE SHARES, A COPY OF
          WHICH MAY BE OBTAINED AT THE PRINCIPAL OFFICE OF THE ISSUER.  SUCH
          TRANSFER RESTRICTIONS AND RIGHT OF FIRST REFUSAL ARE BINDING ON
          TRANSFEREES OF THESE SHARES.

          (b)  Stop-Transfer Notices.  Optionee agrees that, in order to ensure
               ---------------------
compliance with the restrictions referred to herein, the Company may issue
appropriate "stop transfer" instructions to its transfer agent, if any, and
that, if the Company  transfers its own securities, it may make appropriate
notations to the same effect in its own records.

          (c)  Refusal to Transfer.  The Company shall not be required (i) to
               -------------------
transfer on its books any Shares that have been sold or otherwise transferred in
violation of any of the provisions of this Agreement or (ii) to treat as owner
of such Shares or to accord the right to vote or pay dividends to any purchaser
or other transferee to whom such Shares shall have been so transferred.

     8.   Successors and Assigns.  The Company may assign any of its rights
          ----------------------
under this Agreement to single or multiple assignees, and this Agreement shall
inure to the benefit of the successors and assigns of the Company. Subject to
the restrictions on transfer herein set forth, this Agreement shall be binding
upon Optionee and his or her heirs, executors, administrators, successors and
assigns.

                                      -3-
<PAGE>

     9.   Interpretation.  Any dispute regarding the interpretation of this
          --------------
Agreement shall be submitted by Optionee or by the Company forthwith to the
Administrator which shall review such dispute at its next regular meeting. The
resolution of such a dispute by the Administrator shall be final and binding on
all parties.

     10.  Governing Law; Severability.  This Agreement is governed by the
          ---------------------------
internal substantive laws, but not the choice of law rules, of California.

     11.  Entire Agreement.  The Plan and Option Agreement are incorporated
          ----------------
herein by reference. This Agreement, the Plan, the Restricted Stock Purchase
Agreement, the Option Agreement and the Investment Representation Statement
constitute the entire agreement of the parties with respect to the subject
matter hereof and supersede in their entirety all prior undertakings and
agreements of the Company and Optionee with respect to the subject matter
hereof, and may not be modified adversely to the Optionee's interest except by
means of a writing signed by the Company and Optionee.

Submitted by:                       Accepted by:

OPTIONEE:                           NUMERICAL TECHNOLOGIES, INC.

/s/ Roger Sturgeon                  /s/ Yagyensh C. Pati
_______________________________     _______________________________
Signature                           By

Roger Sturgeon                      President & CEO
-------------------------------     _______________________________
Print Name                          Its

Address:                            Address:
-------                             -------

16490 Lucky Road                    70 West Plumeria Drive
-------------------------------
                                    San Jose, CA  95134-2134

Los Gatos, CA  95030
-------------------------------

                                    February 1, 2000
                                    -------------------------------
                                    Date Received

                                      -4-
<PAGE>

                                   EXHIBIT B
                                   ---------

                      INVESTMENT REPRESENTATION STATEMENT

OPTIONEE       :       ROGER STUREGON

COMPANY        :       NUMERICAL TECHNOLOGIES, INC.

SECURITY       :       COMMON STOCK

AMOUNT         :       150,000 SHARES

DATE           :       FEBRUARY 1, 2000

     In connection with the purchase of the above-listed Securities, the
undersigned Optionee represents to the Company the following:

          (a)  Optionee is aware of the Company's business affairs and financial
condition and has acquired sufficient information about the Company to reach an
informed and knowledgeable decision to acquire the Securities. Optionee is
acquiring these Securities for investment for Optionee's own account only and
not with a view to, or for resale in connection with, any distribution" thereof
within the meaning of the Securities Act of 1933, as amended (the "Securities
Act").

          (b)  Optionee acknowledges and understands that the Securities
constitute "restricted securities" under the Securities Act and have not been
registered under the Securities Act in reliance upon a specific exemption
therefrom, which exemption depends upon, among other things, the bona fide
nature of Optionee's investment intent as expressed herein. In this connection,
Optionee understands that, in the view of the Securities and Exchange
Commission, the statutory basis for such exemption may be unavailable if
Optionee's representation was predicated solely upon a present intention to hold
these Securities for the minimum capital gains period specified under tax
statutes, for a deferred sale, for or until an increase or decrease in the
market price of the Securities, or for a period of one year or any other fixed
period in the future. Optionee further understands that the Securities must be
held indefinitely unless they are subsequently registered under the Securities
Act or an exemption from such registration is available. Optionee further
acknowledges and understands that the Company is under no obligation to register
the Securities. Optionee understands that the certificate evidencing the
Securities will be imprinted with a legend which prohibits the transfer of the
Securities unless they are registered or such registration is not required in
the opinion of counsel satisfactory to the Company, and any other legend
required under applicable state securities laws.

          (c)  Optionee is familiar with the provisions of Rule 144, promulgated
under the Securities Act, which, in substance, permits limited public resale of
"restricted securities" acquired, directly or indirectly, from the issuer
thereof (or from an affiliate of such issuer), in a non-public offering subject
to the satisfaction of certain conditions, including, among other things: (1)
the resale occurring not less than one year after the later of the date the
securities were sold by the
<PAGE>

Company or the date they were sold by an affiliate of the Company, within the
meaning of Rule 144; and, in the case of an affiliate, or of a non-affiliate who
has held the securities less than two years, (2) the availability of certain
public information about the Company, (3) the sale being made through a broker
in an unsolicited "broker's transaction" or in transactions directly with a
market maker (as said term is defined under the Securities Exchange Act of
1934), and (4) the amount of securities being sold during any three month period
not exceeding the specified limitations stated therein, if applicable.

          (d)  Optionee further understands that in the event all of the
applicable requirements of or 144 are not satisfied, registration under the
Securities Act, compliance with Regulation A, or some other registration
exemption will be required; and that, notwithstanding the fact that Rule 144 is
not exclusive, the Staff of the Securities and Exchange Commission has expressed
its opinion that persons proposing to sell private placement securities other
than in a registered offering and otherwise than pursuant to Rule 144 will have
a substantial burden of proof in establishing that an exemption from
registration is available for such offers or sales, and that such persons and
their respective brokers who participate in such transactions do so at their own
risk. Optionee understands that no assurances can be given that any such other
registration exemption will be available in such event.

                                    Signature of Optionee:

                                    /s/ Roger Sturgeon
                                    ____________________________________
                                    Date:  February 1, 2000

                                      -2-
<PAGE>

                                  EXHIBIT C-1
                                  -----------

                         NUMERICAL TECHNOLOGIES, INC.

                                2000 STOCK PLAN

                      RESTRICTED STOCK PURCHASE AGREEMENT

     THIS AGREEMENT is made between Roger Sturgeon (the "Purchaser") and
Numerical Technologies, Inc. (the "Company") as of February 1, 2000.

                                   RECITALS
                                   --------

     (1)  Pursuant to the exercise of the stock option granted to Purchaser
under the Company's 2000 Stock Plan (the "Plan") and pursuant to the Stock
Option Agreement (the "Option Agreement") dated February 1, 2000 by and between
the Company and Purchaser with respect to such grant, which Plan and Option
Agreement are hereby incorporated by reference, Purchaser has elected to
purchase 150,000 of those shares which have not become vested under the vesting
schedule set forth in the Option Agreement ("Unvested Shares"). The Unvested
Shares and the shares subject to the Option Agreement which have become vested
are sometimes collectively referred to herein as the "Shares".

     (2)  As required by the Option Agreement, as a condition to Purchaser's
election to exercise the option, Purchaser must execute this Restricted Stock
Purchase Agreement, which sets forth the rights and obligations of the parties
with respect to Shares acquired upon exercise of the Option.

     1.   Repurchase Option.
          -----------------

          (a)  If Purchaser's status as a Service Provider is terminated for any
reason, including for cause, death, and disability, the Company shall have the
right and option to purchase from Purchaser, or Purchaser's personal
representative, as the case may be, all of the Purchaser's Unvested Shares as of
the date of such termination at the price paid by the Purchaser for such Shares
(the "Repurchase Option").

          (b)  Upon the occurrence of a termination, the Company may exercise
its Repurchase Option by delivering personally or by registered mail, to
Purchaser (or his transferee or legal representative, as the case may be),
within ninety (90) days of the termination, a notice in writing indicating the
Company's intention to exercise the Repurchase Option and setting forth a date
for closing not later than thirty (30) days from the mailing of such notice. The
closing shall take place at the Company's office. At the closing, the holder of
the certificates for the Unvested Shares being transferred shall deliver the
stock certificate or certificates evidencing the Unvested Shares, and the
Company shall deliver the purchase price therefor.
<PAGE>

          (c)  At its option, the Company may elect to make payment for the
Unvested Shares to a bank selected by the Company. The Company shall avail
itself of this option by a notice in writing to Purchaser stating the name and
address of the bank, date of closing, and waiving the closing at the Company's
office.

          (d)  If the Company does not elect to exercise the Repurchase Option
conferred above by giving the requisite notice within ninety (90) days following
the termination, the Repurchase Option shall terminate.

          (e)  The Repurchase Option shall terminate in accordance with the
Vesting Schedule in Optionee's Option Agreement.

     2.   Transferability of the Shares; Escrow.
          -------------------------------------

          (a)  Purchaser hereby authorizes and directs the secretary of the
Company, or such other person designated by the Company, to transfer the
Unvested Shares as to which the Repurchase Option has been exercised from
Purchaser to the Company.

          (b)  To insure the availability for delivery of Purchaser's Unvested
Shares upon repurchase by the Company pursuant to the Repurchase Option under
Section 1, Purchaser hereby appoints the secretary, or any other person
designated by the Company as escrow agent, as its attorney-in-fact to sell,
assign and transfer unto the Company, such Unvested Shares, if any, repurchased
by the Company pursuant to the Repurchase Option and shall, upon execution of
this Agreement, deliver and deposit with the secretary of the Company, or such
other person designated by the Company, the share certificates representing the
Unvested Shares, together with the stock assignment duly endorsed in blank,
attached hereto as Exhibit C-2. The Unvested Shares and stock assignment shall
                   -----------
be held by the secretary in escrow, pursuant to the Joint Escrow Instructions of
the Company and Purchaser attached as Exhibit C-3 hereto, until the Company
                                      -----------
exercises its purchase right as provided in Section 1, until such Unvested
Shares are vested, or until such time as this Agreement no longer is in effect.
As a further condition to the Company's obligations under this Agreement, the
spouse of the Purchaser, if any, shall execute and deliver to the Company the
Consent of Spouse attached hereto as Exhibit C-4. Upon vesting of the Unvested
                                     -----------
Shares, the escrow agent shall promptly deliver to the Purchaser the certificate
or certificates representing such Shares in the escrow agent's possession
belonging to the Purchaser, and the escrow agent shall be discharged of all
further obligations hereunder; provided, however, that the escrow agent shall
nevertheless retain such certificate or certificates as escrow agent if so
required pursuant to other restrictions imposed pursuant to this Agreement.

          (c)  The Company, or its designee, shall not be liable for any act it
may do or omit to do with respect to holding the Shares in escrow and while
acting in good faith and in the exercise of its judgment.

          (d)  Transfer or sale of the Shares is subject to restrictions on
transfer imposed by any applicable state and federal securities laws. Any
transferee shall hold such Shares subject to all the provisions hereof and the
Exercise Notice executed by the Purchaser with respect to any

                                      -2-
<PAGE>

Unvested Shares purchased by Purchaser and shall acknowledge the same by signing
a copy of this Agreement.

     3.   Ownership, Voting Rights, Duties.  This Agreement shall not affect in
          --------------------------------
any way the ownership, voting rights or other rights or duties of Purchaser,
except as specifically provided herein.

     4.   Legends.  The share certificate evidencing the Shares issued hereunder
          -------
shall be endorsed with the following legend (in addition to any legend required
under applicable state securities laws):

     THE SHARES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO CERTAIN
RESTRICTIONS UPON TRANSFER AND RIGHTS OF REPURCHASE AS SET FORTH IN AN AGREEMENT
BETWEEN THE COMPANY AND THE STOCKHOLDER, A COPY OF WHICH IS ON FILE WITH THE
SECRETARY OF THE COMPANY.

     5.   Adjustment for Stock Split. All references to the number of Shares and
          --------------------------
the purchase price of the Shares in this Agreement shall be appropriately
adjusted to reflect any stock split, stock dividend or other change in the
Shares which may be made by the Company after the date of this Agreement.

     6.   Notices. Notices required hereunder shall be given in person or by
          -------
registered mail to the address of Purchaser shown on the records of the Company,
and to the Company at their respective principal executive offices.

     7.   Survival of Terms. This Agreement shall apply to and bind Purchaser
          -----------------
and the Company and their respective permitted assignees and transferees, heirs,
legatees, executors, administrators and legal successors.

     8.   Section 83(b) Election. Purchaser hereby acknowledges that he or she
          ----------------------
has been informed that, with respect to the exercise of an Option for unvested
Shares, an election may be filed by the Purchaser with the Internal Revenue
Service, within 30 days of the purchase of the Shares, electing pursuant to
         --------------
Section 83(b) of the Code to be taxed currently on any difference between the
purchase price of the Shares and their Fair Market Value on the date of
purchase. In the case of a Nonstatutory Stock Option, this will result in a
recognition of taxable income to the Purchaser on the date of exercise, measured
by the excess, if any, of the fair market value of the Shares, at the time the
Option is exercised over the purchase price for the Shares. Absent such an
election, taxable income will be measured and recognized by Purchaser at the
time or times on which the Company's Repurchase Option lapses. In the case of an
Incentive Stock Option, such an election will result in a recognition of income
to the Purchaser for alternative minimum tax purposes on the date of exercise,
measured by the excess, if any, of the fair market value of the Shares, at the
time the option is exercised, over the purchase price for the Shares. Absent
such an election, alternative minimum taxable income will be measured and
recognized by Purchaser at the time or times on which the Company's Repurchase
Option lapses. Purchaser is strongly encouraged to seek the advice of his or her
own tax consultants in connection with the purchase of the Shares and the
advisability of filing

                                      -3-
<PAGE>

of the Election under Section 83(b) of the Code. A form of Election under
Section 83(b) is attached hereto as Exhibit C-5 for reference.
                                    -----------

     PURCHASER ACKNOWLEDGES THAT IT IS PURCHASER'S SOLE RESPONSIBILITY AND NOT
THE COMPANY'S TO FILE TIMELY THE ELECTION UNDER SECTION 83(b), EVEN IF PURCHASER
REQUESTS THE COMPANY OR ITS REPRESENTATIVE TO MAKE THIS FILING ON PURCHASER'S
BEHALF.

     9.   Representations.  Purchaser has reviewed with his own tax advisors the
          ---------------
federal, state, local and foreign tax consequences of this investment and the
transactions contemplated by this Agreement. Purchaser is relying solely on such
advisors and not on any statements or representations of the Company or any of
its agents. Purchaser understands that he (and not the Company) shall be
responsible for his own tax liability that may arise as a result of this
investment or the transactions contemplated by this Agreement.

     10.  Governing Law.  This Agreement shall be governed by the internal
          -------------
substantive laws, but not the choice of law rules, of California.

     Purchaser represents that he has read this Agreement and is familiar with
its terms and provisions.  Purchaser hereby agrees to accept as binding,
conclusive and final all decisions or interpretations of the Board upon any
questions arising under this Agreement.

                                      -4-
<PAGE>

     IN WITNESS WHEREOF, this Agreement is deemed made as of the date first set
forth above.

                                    "COMPANY"

                                    NUMERICAL TECHNOLOGIES, INC

                                    /s/ Yagyensh C. Pati
                                    _____________________________________
                                    By

                                    President & CEO
                                    _____________________________________
                                    Title

                                    "PURCHASER"

                                    /s/ Roger Sturgeon
                                    _____________________________________
                                    Signature

                                    Roger Sturgeon
                                    -------------------------------------
                                    Printed Name

                                    _____________________________________
                                    Soc. Sec. No.

                                    Address:
                                    -------

                                    16490 Lucky Road
                                    -------------------------------------

                                    Los Gatos, CA  95030
                                    -------------------------------------

                                      -5-
<PAGE>

                                  EXHIBIT C-2
                                  -----------

                     ASSIGNMENT SEPARATE FROM CERTIFICATE

     FOR VALUE RECEIVED I, __________________________, hereby sell, assign and
transfer unto Numerical Technologies, Inc. (__________) shares of the Common
Stock of Numerical Technologies, Inc. standing in my name of the books of said
corporation represented by Certificate No. _____ herewith and do hereby
irrevocably constitute and appoint         to transfer the said stock on the
books of the within named corporation with full power of substitution in the
premises.

     This Stock Assignment may be used only in accordance with the Restricted
Stock Purchase Agreement between Numerical Technologies, Inc. and the
undersigned dated ______________, _____.

Dated: _______________, ______

               /s/ Roger Sturgeon
     Signature:________________________________

INSTRUCTIONS: Please do not fill in any blanks other than the signature line.
The purpose of this assignment is to enable the Company to exercise its
"repurchase option," as set forth in the Agreement, without requiring additional
signatures on the part of the Purchaser.
<PAGE>

                                  EXHIBIT C-3
                                  -----------

                           JOINT ESCROW INSTRUCTIONS

                                                                February 1, 2000

Numerical Technologies, Inc.
70 West Plumeria Drive
San Jose, CA  95134-2134
Attention:  Secretary

Dear__________:

     As Escrow Agent for both Numerical Technologies, Inc. (the "Company"), and
the undersigned purchaser of stock of the Company (the "Purchaser"), you are
hereby authorized and directed to hold the documents delivered to you pursuant
to the terms of that certain Restricted Stock Purchase Agreement ("Agreement")
between the Company and the undersigned, in accordance with the following
instructions:

     1.   In the event the Company and/or any assignee of the Company (referred
to collectively for convenience herein as the "Company") exercises the Company's
repurchase option set forth in the Agreement, the Company shall give to
Purchaser and you a written notice specifying the number of shares of stock to
be purchased, the purchase price, and the time for a closing hereunder at the
principal office of the Company. Purchaser and the Company hereby irrevocably
authorize and direct you to close the transaction contemplated by such notice in
accordance with the terms of said notice.

     2.   At the closing, you are directed (a) to date the stock assignments
necessary for the transfer in question, (b) to fill in the number of shares
being transferred, and (c) to deliver same, together with the certificate
evidencing the shares of stock to be transferred, to the Company or its
assignee, against the simultaneous delivery to you of the purchase price (by
cash, a check, or some combination thereof) for the number of shares of stock
being purchased pursuant to the exercise of the Company's repurchase option.

     3.   Purchaser irrevocably authorizes the Company to deposit with you any
certificates evidencing shares of stock to be held by you hereunder and any
additions and substitutions to said shares as defined in the Agreement.
Purchaser does hereby irrevocably constitute and appoint you as Purchaser's
attorney-in-fact and agent for the term of this escrow to execute with respect
to such securities all documents necessary or appropriate to make such
securities negotiable and to complete any transaction herein contemplated,
including but not limited to the filing with any applicable state blue sky
authority of any required applications for consent to, or notice of transfer of,
the securities. Subject to the provisions of this paragraph 3, Purchaser shall
exercise all rights and privileges of a stockholder of the Company while the
stock is held by you.
<PAGE>

     4.   Upon written request of the Purchaser, but no more than once per
calendar year, unless the Company's repurchase option has been exercised, you
will deliver to Purchaser a certificate or certificates representing so many
shares of stock as are not then subject to the Company's repurchase option.
Within 120 days after cessation of Purchaser's continuous employment by or
services to the Company, or any parent or subsidiary of the Company, you will
deliver to Purchaser a certificate or certificates representing the aggregate
number of shares held or issued pursuant to the Agreement and not purchased by
the Company or its assignees pursuant to exercise of the Company's repurchase
option.

     5.   If at the time of termination of this escrow you should have in your
possession any documents, securities, or other property belonging to Purchaser,
you shall deliver all of the same to Purchaser and shall be discharged of all
further obligations hereunder.

     6.   Your duties hereunder may be altered, amended, modified or revoked
only by a writing signed by all of the parties hereto.

     7.   You shall be obligated only for the performance of such duties as are
specifically set forth herein and may rely and shall be protected in relying or
refraining from acting on any instrument reasonably believed by you to be
genuine and to have been signed or presented by the proper party or parties. You
shall not be personally liable for any act you may do or omit to do hereunder as
Escrow Agent or as attorney-in-fact for Purchaser while acting in good faith,
and any act done or omitted by you pursuant to the advice of your own attorneys
shall be conclusive evidence of such good faith.

     8.   You are hereby expressly authorized to disregard any and all warnings
given by any of the parties hereto or by any other person or corporation,
excepting only orders or process of courts of law and are hereby expressly
authorized to comply with and obey orders, judgments or decrees of any court. In
case you obey or comply with any such order, judgment or decree, you shall not
be liable to any of the parties hereto or to any other person, firm or
corporation by reason of such compliance, notwithstanding any such order,
judgment or decree being subsequently reversed, modified, annulled, set aside,
vacated or found to have been entered without jurisdiction.

     9.   You shall not be liable in any respect on account of the identity,
authorities or rights of the parties executing or delivering or purporting to
execute or deliver the Agreement or any documents or papers deposited or called
for hereunder.

     10.  You shall not be liable for the outlawing of any rights under the
Statute of Limitations with respect to these Joint Escrow Instructions or any
documents deposited with you.

     11.  You shall be entitled to employ such legal counsel and other experts
as you may deem necessary properly to advise you in connection with your
obligations hereunder, may rely upon the advice of such counsel, and may pay
such counsel reasonable compensation therefor.

     12.  Your responsibilities as Escrow Agent hereunder shall terminate if you
shall cease to be an officer or agent of the Company or if you shall resign by
written notice to each party. In the event of any such termination, the Company
shall appoint a successor Escrow Agent.

                                      -2-
<PAGE>

     13.  If you reasonably require other or further instruments in connection
with these Joint Escrow Instructions or obligations in respect hereto, the
necessary parties hereto shall join in furnishing such instruments.

     14.  It is understood and agreed that should any dispute arise with respect
to the delivery and/or ownership or right of possession of the securities held
by you hereunder, you are authorized and directed to retain in your possession
without liability to anyone all or any part of said securities until such
disputes shall have been settled either by mutual written agreement of the
parties concerned or by a final order, decree or judgment of a court of
competent jurisdiction after the time for appeal has expired and no appeal has
been perfected, but you shall be under no duty whatsoever to institute or defend
any such proceedings.

     15.  Any notice required or permitted hereunder shall be given in writing
and shall be deemed effectively given upon personal delivery or upon deposit in
the United States Post Office, by registered or certified mail with postage and
fees prepaid, addressed to each of the other parties thereunto entitled at the
following addresses or at such other addresses as a party may designate by ten
days' advance written notice to each of the other parties hereto.

          COMPANY:       Numerical Technologies, Inc.
                         70 West Plumeria Drive
                         San Jose, CA  95134-2134
                         Attention:  Secretary

          PURCHASER:     Roger Sturgeon
                         16490 Lucky Road
                         Los Gatos, CA  95030

          ESCROW AGENT:  Wilson Sonsini Goodrich & Rosati
                         650 Page Mill Road
                         Palo Alto, CA  94304

     16.  By signing these Joint Escrow Instructions, you become a party hereto
only for the purpose of said Joint Escrow Instructions; you do not become a
party to the Agreement.

     17.  This instrument shall be binding upon and inure to the benefit of the
parties hereto, and their respective successors and permitted assigns.

                                      -3-
<PAGE>

     18.  These Joint Escrow Instructions shall be governed by the internal
substantive laws, but not the choice of law rules, of California.

                                    NUMERICAL TECHNOLOGIES, INC.

                                    /s/ Yagyensh C. Pati
                                    _____________________________________
                                    By

                                    President & CEO
                                    _____________________________________
                                    Title

                                    PURCHASER

                                    /s/ Roger Sturgeon
                                    _____________________________________
                                    Signature

                                    Roger Sturgeon
                                    -------------------------------------
                                    Typed or Printed Name

                                    ESCROW AGENT

                                    WILSON SONSINI GOODRICH & ROSATI

                                    /s/ John V. Roos
                                    _____________________________________
                                    By

                                    Member
                                    _____________________________________
                                    Title

                                      -4-
<PAGE>

                                  EXHIBIT C-4
                                 ------------

                               CONSENT OF SPOUSE
                               -----------------
        Isobel Sturgeon
     I, ____________________, spouse of Roger Sturgeon, have read and approve
the foregoing Agreement.  In consideration of granting of the right to my spouse
to purchase shares of Numerical Technologies, Inc., as set forth in the
Agreement, I hereby appoint my spouse as my attorney-in-fact in respect to the
exercise of any rights under the Agreement and agree to be bound by the
provisions of the Agreement insofar as I may have any rights in said Agreement
or any shares issued pursuant thereto under the community property laws or
similar laws relating to marital property in effect in the state of our
residence as of the date of the signing of the foregoing Agreement.

       February 1
Dated: _______________,  2000

                                             /s/ Isobel Sturgeon
                                             ___________________________________
<PAGE>

                                  EXHIBIT C-5
                                  -----------

                         ELECTION UNDER SECTION 83(b)
                         -----------------------------
                     OF THE INTERNAL REVENUE CODE OF 1986
                     ------------------------------------

The undersigned taxpayer hereby elects, pursuant to Sections 55 and 83(b) of the
Internal Revenue Code of 1986, as amended, to include in taxpayer's gross income
or alternative minimum taxable income, as the case may be, for the current
taxable year the amount of any compensation taxable to taxpayer in connection
with taxpayer's receipt of the property described below:

1.   The name, address, taxpayer identification number and taxable year of the
undersigned are as follows:

     NAME:               TAXPAYER: Roger Sturgeon     SPOUSE: Isobel Sturgeon

     ADDRESS:            16490 Lucky Road, Los Gatos, CA 95030

     IDENTIFICATION NO.: TAXPAYER: ###-##-####        SPOUSE: ###-##-####

     TAXABLE YEAR:       2000

2.   The property with respect to which the election is made is described as
follows: 150,000 shares (the "Shares") of the Common Stock of Numerical
Technologies, Inc. (the "Company").

3.   The date on which the property was transferred is:  Feb. 1, 2000.

4.   The property is subject to the following restrictions:

     The Shares may not be transferred and are subject to forfeiture under the
terms of an agreement between the taxpayer and the Company.  These restrictions
lapse upon the satisfaction of certain conditions contained in such agreement.

5.   The fair market value at the time of transfer, determined without regard to
any restriction other than a restriction which by its terms will never lapse, of
such property is:
     $600,000.

6.   The amount (if any) paid for such property is:
     $600,000.

The undersigned has submitted a copy of this statement to the person for whom
the services were performed in connection with the undersigned's receipt of the
above-described property.  The transferee of such property is the person
performing the services in connection with the transfer of said property.

The undersigned understands that the foregoing election may not be revoked
--------------------------------------------------------------------------
except with the consent of the Commissioner.
-------------------------------------------

                                        /s/ Roger Sturgeon
Dated:  Feb. 1,2000                     ________________________________________
                                        Taxpayer

The undersigned spouse of taxpayer joins in this election.

                                        /s/ Isobel Sturgeon
Dated:  Feb. 1,2000                     ________________________________________

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