Document:

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                                                                    EXHIBIT 10.4

                             SIMPLEX SOLUTIONS, INC.
                            2001 INCENTIVE STOCK PLAN

         1. Purposes of the Plan. The purposes of this 2001 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 of the Plan.

                  (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 foreign country or jurisdiction where Options or Stock Purchase Rights are,
or will be, 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 of the Plan.

                  (f) "Common Stock" means the common stock of the Company.

                  (g) "Company" means Simplex Solutions, Inc., a Delaware
corporation.

                  (h) "Consultant" means any person, including an advisor,
engaged by the Company or a Parent or Subsidiary to render services to such
entity.

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

                  (j) "Disability" means total and permanent disability as
defined in Section 22(e)(3) of the Code.
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                  (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 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, then three (3) months following the 91st 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 on the day 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, the Fair
Market Value of a Share of Common Stock shall be the mean between the high bid
and low asked prices for the Common Stock on the day of determination, as
reported in The Wall Street Journal or such other source as the Administrator
deems reliable; or

                               (iii) In the absence of an established market for
the Common Stock, the Fair Market Value 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 and the regulations promulgated thereunder.

                  (o) "Inside Director" means a Director who is an Employee.

                  (p) "IPO Effective Date" means the date upon which the
Securities and Exchange Commission declares the initial public offering of the
Company's common stock as effective.

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

                  (r) "Notice of Grant" means a written or electronic notice
evidencing certain terms and conditions of an individual Option or Stock
Purchase Right grant. The Notice of Grant is part of the Option Agreement.

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                  (s) "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.

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

                  (u) "Option Agreement" means an 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.

                  (v) "Option Exchange Program" means a program whereby
outstanding Options are surrendered in exchange for Options with a lower
exercise price.

                  (w) "Optioned Stock" means the Common Stock subject to an
Option or Stock Purchase Right.

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

                  (y) "Outside Director" means a Director who is not an
Employee.

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

                  (aa) "Plan" means this 2001 Incentive Stock Plan, as amended
and restated.

                  (bb) "Restricted Stock" means shares of Common Stock acquired
pursuant to a grant of Stock Purchase Rights under Section 11 of the Plan.

                  (cc) "Restricted Stock Purchase Agreement" means a written
agreement between the Company and the Optionee evidencing the terms and
restrictions applying to stock purchased under a Stock Purchase Right. The
Restricted Stock Purchase Agreement is subject to the terms and conditions of
the Plan and the Notice of Grant.

                  (dd) "Rule 16b-3" means Rule 16b-3 of the Exchange Act or any
successor to Rule 16b-3, as in effect when discretion is being exercised with
respect to the Plan.

                  (ee) "Section 16(b) " means Section 16(b) of the Exchange Act.

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

                  (gg) "Share" means a share of the Common Stock, as adjusted in
accordance with Section 14 of the Plan.

                  (hh) "Stock Purchase Right" means the right to purchase Common
Stock pursuant to Section 11 of the Plan, as evidenced by a Notice of Grant.

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

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         3. Stock Subject to the Plan. Subject to the provisions of Section 14
of the Plan, the maximum aggregate number of Shares that may be optioned and
sold under the Plan is 2,400,000 Shares plus (a) any Shares which have been
reserved but not issued under the Company's 1995 Stock Plan (the "1995 Plan") as
of the date of stockholder approval of this Plan, (b) any Shares returned to the
1995 Plan as a result of termination of options or repurchase of Shares issued
under the 1995 Plan and (c) an annual increase to be added on the first day of
the Company's fiscal year beginning in 2002, equal to the lesser of (i)
2,500,000 shares, (ii) 5% of the outstanding shares on such date or (iii) an
amount determined by the Board. 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); provided, however, that Shares that have actually been issued under
the Plan, whether upon exercise of an Option or 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) Procedure.

                               (i) Multiple Administrative Bodies. Different
Committees with respect to different groups of Service Providers may administer
the Plan.

                               (ii) Section 162(m). To the extent that the
Administrator determines it to be desirable to qualify Options granted hereunder
as "performance-based compensation" within the meaning of Section 162(m) of the
Code, the Plan shall be administered by a Committee of two or more "outside
directors" within the meaning of Section 162(m) of the Code.

                               (iii) Rule 16b-3. To the extent desirable to
qualify transactions hereunder as exempt under Rule 16b-3, the transactions
contemplated hereunder shall be structured to satisfy the requirements for
exemption under Rule 16b-3.

                               (iv) Other Administration. Other than as provided
above, the Plan shall be administered by (A) the Board or (B) a Committee, which
committee shall be constituted to satisfy Applicable Laws.

                  (b) Powers of the Administrator. Subject to the provisions of
the Plan, and in the case of a Committee, subject to the specific duties
delegated by the Board to such Committee, 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 be granted hereunder;

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                               (iii) to determine the number of shares of Common
Stock to be covered by each Option and Stock Purchase Right granted hereunder;

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

                               (v) to determine the terms and conditions, not
inconsistent with the terms of the Plan, 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 shares of Common
Stock relating thereto, based in each case on such factors as the Administrator,
in its sole discretion, shall determine;

                               (vi) to reduce the exercise price of any Option
or Stock Purchase Right to the then current Fair Market Value if the Fair Market
Value of the Common Stock covered by such Option or Stock Purchase Right shall
have declined since the date the Option or Stock Purchase Right was granted;

                               (vii) to institute an Option Exchange Program;

                               (viii) to construe and interpret the terms of the
Plan and awards granted pursuant to the Plan;

                               (ix) to establish, amend and rescind rules and
regulations relating to the Plan, including rules and regulations relating to
sub-plans established for the purpose of satisfying applicable foreign laws;

                               (x) to modify or amend each Option or Stock
Purchase Right (subject to Section 16(c) of the Plan), including the
discretionary authority to extend the post-termination exercisability period of
Options longer than is otherwise provided for in the Plan;

                               (xi) 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 minimum 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
an Optionee 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;

                               (xii) to authorize any person to execute on
behalf of the Company any instrument required to effect the grant of an Option
or Stock Purchase Right previously granted by the Administrator;

                               (xiii) to correct any defect, supply any
omission, or reconcile any inconsistency in the Plan, or in any Option
Agreement, in a manner and to the extent it shall deem necessary, all of which
determinations and interpretations made by the Administrator shall be conclusive
and binding on all Optionees, any other holders of Options and on their legal
representatives and beneficiaries; and

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                               (xiv) except to the extent prohibited by, or
impermissible in order to obtain treatment desired by the Administrator under,
applicable law or rule, to allocate or delegate all or any portion of its powers
and responsibilities to any one or more of its members or to any person(s)
selected by it, subject to revocation or modification by the Administrator of
such allocation or delegation.

                               (xv) to make all other determinations deemed
necessary or advisable for administering the Plan.

                  (c) Effect of Administrator's Decision. The Administrator's
decisions, determinations and interpretations shall be final and binding on all
Optionees and any other holders of Options or Stock Purchase Rights.

         5. Eligibility. Nonstatutory Stock Options and Stock Purchase Rights
may be granted to Service Providers. Incentive Stock Options may be granted only
to Employees.

         6. Limitations.

                  (a) 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 6(a), 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.

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

                  (c) The following limitations shall apply to grants of
Options:

                               (i) No Service Provider shall be granted, in any
fiscal year of the Company, Options to purchase more than 500,000 Shares.

                               (ii) In connection with his or her initial
service, a Service Provider may be granted Options to purchase up to an
additional 1,000,000 Shares, which shall not count against the limit set forth
in subsection (i) above.

                               (iii) The foregoing limitations shall be adjusted
proportionately in connection with any change in the Company's capitalization as
described in Section 14.

                               (iv) If an Option is cancelled in the same fiscal
year of the Company in which it was granted (other than in connection with a
transaction described in Section 14), the cancelled Option will be counted
against the limits set forth in subsections (i) and (ii) above. For

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this purpose, if the exercise price of an Option is reduced, the transaction
will be treated as a cancellation of the Option and the grant of a new Option.

         7. Term of Plan. Subject to Section 20 of the 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 terminated earlier under Section 16 of the Plan.

         8. Term of Option. The term of each Option shall be stated in the
Option Agreement. In the case of an Incentive Stock Option, the term shall be
ten (10) years from the date of grant or such shorter term as may be provided in
the Option Agreement. Moreover, in the case of an Incentive Stock Option granted
to an Optionee who, at the time the Incentive Stock Option is granted, owns
stock representing more than ten percent (10%) of the total combined voting
power of all classes of stock of the Company or any Parent or Subsidiary, the
term of the Incentive Stock Option shall be five (5) years from the date of
grant or such shorter term as may be provided in the Option Agreement.

         9. Option Exercise Price and Consideration.

                  (a) Exercise Price. The per share exercise price for the
Shares to be issued pursuant to exercise of an Option shall be determined by the
Administrator, subject to the following:

                               (i) In the case of an Incentive Stock Option

                                    (A) granted to an Employee who, at the time
the Incentive Stock 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 per Share exercise price shall be no less than 110% of
the Fair Market Value per Share on the date of grant.

                                    (B) granted to any Employee other than an
Employee described in paragraph (A) immediately above, 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,
the per Share exercise price shall be determined by the Administrator. In the
case of a Nonstatutory Stock Option intended to qualify as "performance-based
compensation" within the meaning of Section 162(m) of the Code, the per Share
exercise price shall be no less than 100% 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 of less than 100% of the Fair Market
Value per Share on the date of grant pursuant to a merger or other corporate
transaction.

                  (b) Waiting Period and Exercise Dates. At the time an Option
is granted, the Administrator shall fix the period within which the Option may
be exercised and shall determine any conditions that must be satisfied before
the Option may be exercised.

                  (c) Form of Consideration. The Administrator shall determine
the acceptable form of consideration for exercising an Option, including the
method of payment. In the case of an

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Incentive Stock Option, the Administrator shall determine the acceptable form of
consideration at the time of grant. Such consideration may consist entirely of:

                               (i) cash;

                               (ii) check;

                               (iii) promissory note;

                               (iv) other Shares, provided Shares acquired from
the Company, (A) have been owned by the Optionee for more than six (6) months on
the date of surrender, and (B) have a Fair Market Value on the date of surrender
equal to the aggregate exercise price of the Shares as to which said Option
shall be exercised;

                               (v) consideration received by the Company under a
cashless exercise program implemented by the Company in connection with the
Plan;

                               (vi) a reduction in the amount of any Company
liability to the Optionee, including any liability attributable to the
Optionee's participation in any Company-sponsored deferred compensation program
or arrangement;

                               (vii) any combination of the foregoing methods of
payment; or

                               (viii) such other consideration and method of
payment for the issuance of Shares to the extent permitted by Applicable Laws.

         10. Exercise of Option.

                  (a) Procedure for Exercise; Rights as a Stockholder. Any
Option granted hereunder shall be exercisable according to the terms of the Plan
and at such times and under such conditions as determined by the Administrator
and set forth in the Option Agreement. 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 or
in the name of a family trust of which the Optionee is a trustee. 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 to vote
or receive dividends or any other rights as a stockholder shall exist with
respect to the Optioned Stock, notwithstanding the exercise of the Option. The
Company shall issue (or cause to be issued) such Shares promptly after the
Option is exercised; provided that if the Company shall be advised by counsel
that certain requirements under the Federal, state or foreign securities laws
must be met before Shares may be issued under this Plan, the Company shall
notify all persons who have been

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issued Options, and the Company shall have no liability for failure to issue
Shares under any exercise of Options because of delay while such requirements
are being met or the inability of the Company to comply with such requirements.
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
14 of the Plan.

                  Exercising an Option in any manner shall decrease 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, other than upon the Optionee's death
or Disability, the Optionee may exercise his or her Option within such period of
time as is specified in the Option Agreement 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 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 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 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 (but in no event later than the expiration of the term
of such Option as set forth in the Notice of Grant), by the Optionee's estate or
by a person who acquires the right to exercise the Option by bequest or
inheritance, but only to the extent that the Option is vested on the date of
death. 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 his or
her entire Option, the Shares covered by the unvested portion of the Option
shall immediately revert to the Plan. The Option may be exercised by the
executor or administrator of the Optionee's estate or, if none, by the person(s)
entitled to exercise the Option under the Optionee's will or the laws of descent
or distribution. 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.

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         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, by means of a Notice of Grant,
of the terms, conditions and restrictions related to the offer, including the
number of Shares that the offeree shall be entitled to purchase, the price to be
paid, and the time within which the offeree must accept such offer. 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 a rate determined by the
Administrator.

                  (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 Stockholder. Once the Stock Purchase Right is
exercised, the purchaser shall have the rights equivalent to those of a
stockholder, and shall be a stockholder when his or her purchase is entered upon
the records of the duly authorized transfer agent of the Company. No adjustment
will 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 14
of the Plan.

         12. Non-Transferability of Options and Stock Purchase Rights. Unless
determined otherwise by the Administrator, an Option or Stock Purchase Right 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. If the
Administrator makes an Option or Stock Purchase Right transferable, such Option
or Stock Purchase Right shall contain such additional terms and conditions as
the Administrator deems appropriate.

         13. Formula Option Grants to Outside Directors. Outside Directors shall
be automatically granted Options each year in accordance with the following
provisions:

                  (a) All Options granted pursuant to this Section shall be
Nonstatutory Stock Options and, except as otherwise provided herein, shall be
subject to the other terms and conditions of the Plan.

                  (b) Each person who first becomes an Outside Director on or
after the IPO Effective Date, whether through election by the stockholders of
the Company or appointment by the Board to fill a vacancy, shall be
automatically granted an Option to purchase [__________] Shares (the "First
Option") on the date he or she first becomes an Outside Director; provided,
however, that

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an Inside Director who ceases to be an Inside Director but who remains a
Director shall not receive a First Option.

                  (c) Each Outside Director shall be automatically granted an
Option to purchase [_________] Shares (a "Subsequent Option") following each
annual meeting of the stockholders of the Company, except in the case of the
first such annual meeting after the IPO Effective Date if such annual meeting is
held within six (6) months of the IPO Effective Date, if as of such date, he or
she shall continue to serve on the Board and shall have served on the Board for
at least the preceding six (6) months.

                  (d) Notwithstanding the provisions of subsections (b) and (c)
hereof, any exercise of an Option granted before the Company has obtained
stockholder approval of the Plan in accordance with Section 20 hereof shall be
conditioned upon obtaining such stockholder approval of the Plan in accordance
with Section 20 hereof.

                  (e) The terms of each First Option granted pursuant to this
Section shall be as follows:

                               (i) the term of the First Option shall be ten
(10) years.

                               (ii) the exercise price per Share shall be 100%
of the Fair Market Value per Share on the date of grant of the First Option.

                               (iii) the First Option shall vest as to ______ of
the Shares subject to the First Option on each anniversary of its date of grant
provided that the Optionee continues to serve as a Director on such date.

                  (f) The terms of each Subsequent Option granted pursuant to
this Section shall be as follows:

                               (i) the term of the Subsequent Option shall be
ten (10) years.

                               (ii) the exercise price per Share shall be 100%
of the Fair Market Value per Share on the date of grant of the Subsequent
Option.

                               (iii) the Subsequent Option shall vest as to
[_______] of the Shares subject to the Subsequent Option on the [___]
anniversary of its date of grant provided that the Optionee continues to serve
as a Director on such date.

         14. Adjustments Upon Changes in Capitalization, Dissolution, Merger or
Asset Sale.

                  (a) Changes in Capitalization. Subject to any required action
by the stockholders of the Company, the number of shares of Common Stock covered
by each outstanding Option and Stock Purchase Right, 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, the number of shares that may be added annually to the shares
reserved under the Plan (pursuant to Section 3(a)(i)), the number of shares
which may be granted pursuant to the

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automatic grant provisions of Section 13, 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 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; provided, however,
that 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 until ten (10) days prior to such
transaction as to all of the Optioned Stock covered thereby, including Shares as
to which the Option 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. With respect
to Options granted to an Outside Director pursuant to Section 13 that are
assumed or substituted for, if following such assumption or substitution the
Optionee's status as a Director or a director of the successor corporation, as
applicable, is terminated other than upon a voluntary resignation by the
Optionee, then the Optionee shall fully vest in and have the right to exercise
the Option as to all of the Optioned Stock, including Shares as to which it
would not otherwise be vested or exercisable.

                  In the event that the successor corporation refuses to assume
or substitute for the Option or Stock Purchase Right, the Optionee shall fully
vest in and have the right to exercise the Option or Stock Purchase Right as to
all of the Optioned Stock, including Shares as to which it would not otherwise
be vested or exercisable. If an Option or Stock Purchase Right becomes fully
vested and exercisable in lieu of assumption or substitution in the event of a
merger or sale of assets, the Administrator shall notify the Optionee in writing
or electronically that the Option or Stock Purchase Right shall be fully vested
and exercisable for a period of fifteen (15) days from the date of such notice,
and the Option or Stock Purchase Right shall terminate upon the expiration of
such period.

                  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

                                      -12-
<PAGE>   13
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.

         15. Date of Grant. The date of grant of an Option or Stock Purchase
Right shall be, for all purposes, the date on which the Administrator makes the
determination granting such Option or Stock Purchase Right, or such other later
date as is determined by the Administrator. Notice of the determination shall be
provided to each Optionee within a reasonable time after the date of such grant.

         16. Amendment and Termination of the Plan.

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

                  (b) Stockholder Approval. The Company shall obtain stockholder
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.

         17. Conditions Upon Issuance of Shares.

                  (a) Legal Compliance. Shares shall not be issued pursuant to
the exercise of an Option or Stock Purchase Right unless the exercise of such
Option or Stock Purchase Right 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 or Stock Purchase Right, the Company may require the person
exercising such Option or Stock Purchase Right 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.

                                      -13-
<PAGE>   14
         18. 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.

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

         20. Stockholder Approval. The Plan shall be subject to approval by the
stockholders of the Company within twelve (12) months after the date the Plan is
adopted. Such stockholder approval shall be obtained in the manner and to the
degree required under Applicable Laws.

                                      -14-
<PAGE>   15
                                   APPENDIX A

                         Rules for French Option Grants

         The following rules shall apply in the case of Option grants to French
residents.

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

                  (a) "Applicable Laws" means the legal requirements relating to
the administration of stock option plans under French corporate, securities, and
tax laws.

                  (b) "Disability" means total and permanent disability, as
defined under Applicable Laws.

                  (c) "Employee" means any person, including officers and
Directors, employed by the Company or any Parent or Subsidiary of the Company,
(i) who does not own more than 10% of the voting power of all classes of stock
of the Company, or any Parent or Subsidiary of the Company, and (ii) who is a
resident of the Republic of France.

                  (d) "Fair Market Value" means, as of any date, the dollar
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 of the Nasdaq Stock Market, its Fair Market Value shall be the
average quotation price for the last 20 days preceding the date of determination
for such stock (or the average closing bid for such 20 day period, if no sales
were reported) as quoted on such exchange or system and reported in The Wall
Street Journal or such other source as the Administrator deems reliable;

                  (ii) If the Common Stock is quoted on the Nasdaq Stock market
(but not on the Nasdaq National Market thereof) or 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 for the last 20 days preceding the date 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.

         2. Eligibility. Options granted pursuant to this Appendix A may be
granted only to Employees; provided, however, that the President Directeur
General, the Directeur General and other directors who are also Employees of a
Subsidiary may be granted Options hereunder.

         3. Term of Plan. Options may be granted under this Appendix A from the
date of the adoption of the Plan by the Board. It shall continue in effect until
the date five years from the date of its adoption, unless terminated earlier
under Section 16 of the Plan.

         4. Option Price. The Option price for the Shares to be issued pursuant
to exercise of an Option shall be determined by the Administrator upon the date
of grant of the Option and stated in

<PAGE>   16
the Option Agreement, but in no event shall be lower than one hundred percent
(100%) of the Fair Market Value on the date the Option is granted. The Option
Price cannot be modified while the Option is outstanding, except as required by
Applicable Laws.

         5. Exercise of Option; Restriction on Sale.

                  (a) Options granted hereunder may be exercised at any time
after the second anniversary of the date of grant (the "Initial Exercise Date")
to the extent they have vested. Options granted hereunder shall vest, subject to
Optionee's continuing status as an Employee on such dates, in accordance with
the following vesting schedule: 50% of the Shares subject to the Option shall
vest on the second (2nd) anniversary of the Option's date of grant (the "Initial
Exercise Date") and 1/48th of the Shares subject to the Option shall vest each
month thereafter, so that 100% of the Optioned Stock shall be exercisable after
four (4) years.

                  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
required 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
to vote or receive dividends or any other rights as a stockholder 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 14 of the Plan.

                  (b) The Shares subject to this Option may not be transferred,
assigned or hypothecated in any manner otherwise than by will or by the laws of
descent or distribution before the date three (3) years from the Initial
Exercise Date; provided, however, that the duration of this restriction on sale
shall be automatically adjusted to conform with any changes to the holding
period required for favorable tax and social security treatment under Applicable
Laws.

                  (c) Termination of Employment Relationship. In the event that
an Optionee's status as an Employee terminates (other than upon the Optionee's
death or Disability), the Optionee may exercise his or her Option, but only
within such period of time as is determined by the Administrator and only to the
extent that the Optionee's Option has vested at 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). If, at the date of termination, the Optionee's Option has
not fully vested, 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.

                  (d) Disability of Optionee. In the event that an Optionee's
status as an Employee terminates as a result of the Optionee's Disability, the
Optionee may exercise his or her Option at any time within twelve (12) months
from the date of such termination, but only to the extent that the

                                      -2-
<PAGE>   17
Optionee's Option has vested at the date of such termination (and in no event
later than the expiration of the term of such Option as set forth in the Option
Agreement). If, at the date of termination, the Optionee's Option has not fully
vested, the Shares covered by the unexercisable 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.

                  (e) Death of Optionee. In the event of the death of an
Optionee while an Employee, the Option may be exercised at any time within
twelve (12) months following the date of death by the Optionee's estate or by a
person who acquired the right to exercise the Option by bequest or inheritance,
but only to the extent that the Optionee's Option has vested at the date of
death (and in no event later than the expiration of the term of such Option as
set forth in the Option Agreement). If, at the time of death, the Optionee's
Option has not fully vested, the Shares covered by the unexercisable portion of
the Option shall revert to the Plan. If, after death, the Optionee's estate or a
person who acquired the right to exercise the Option by bequest or inheritance
does not exercise the Option within the time specified herein, the Option shall
terminate, and the Shares covered by such Option shall immediately revert to the
Plan.

                                      -3-<PAGE>   1

                                                                    EXHIBIT 10.5

                             SIMPLEX SOLUTIONS, INC.

                        2001 EMPLOYEE STOCK PURCHASE PLAN

         The following constitute the provisions of the Employee Stock Purchase
Plan of Simplex Solutions, Inc.

         1. Purpose. The purpose of the Plan is to provide employees of the
Company and its Designated Subsidiaries with an opportunity to purchase Common
Stock of the Company through accumulated payroll deductions. It is the intention
of the Company to have the Plan qualify as an "Employee Stock Purchase Plan"
under Section 423 of the Code. The provisions of the Plan, accordingly, shall be
construed so as to extend and limit participation in a uniform and
nondiscriminatory basis consistent with the requirements of Section 423.

         2. Definitions.

                  (a) "Administrator" shall mean the Board or any Committee
designated by the Board to administer the plan pursuant to Section 14.

                  (b) "Board" shall mean the Board of Directors of the Company.

                  (c) "Change of Control" shall mean the occurrence of any of
the following events:

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

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

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

                               (iv) A change in the composition of the Board, as
a result of which fewer than a majority of the Directors are Incumbent
Directors. "Incumbent Directors" shall mean Directors who either (A) are
Directors of the Company, as applicable, as of the date hereof, or (B) are
elected, or nominated for election, to the Board with the affirmative votes of
at least a majority of those Directors whose election or nomination was not in
connection with any transaction described
<PAGE>   2
in subsections (i), (ii) or (iii) or in connection with an actual or threatened
proxy contest relating to the election of directors of the Company.

                  (d) "Code" shall mean the Internal Revenue Code of 1986, as
amended.

                  (e) "Committee" means a committee of the Board appointed by
the Board in accordance with Section 14 hereof.

                  (f) "Common Stock" shall mean the common stock of the Company.

                  (g) "Company" shall mean Simplex Solutions, Inc., a Delaware
corporation.

                  (h) "Compensation" shall mean all base straight time gross
earnings, bonuses and 50% of commissions but exclusive of payments for incentive
compensation, overtime, shift premium and other compensation.

                  (i) "Designated Subsidiary" shall mean any Subsidiary selected
by the Administrator as eligible to participate in the Plan.

                  (j) "Eligible Employee" shall mean any individual who is a
common law employee of the Company or any Designated Subsidiary and whose
customary employment with the Company or Designated Subsidiary is at least
twenty (20) hours per week and more than five (5) months in any calendar year.
For purposes of the Plan, the employment relationship shall be treated as
continuing intact while the individual is on sick leave or other leave of
absence approved by the Company. Where the period of leave exceeds 90 days and
the individual's right to reemployment is not guaranteed either by statute or by
contract, the employment relationship shall be deemed to have terminated on the
91st day of such leave.

                  (k) "Exercise Date" shall mean the first Trading Day on or
after May 1st and November 1st of each year. The first Exercise Date under the
Plan shall be the first Trading Day on or after November 1, 2001.

                  (l) "Fair Market Value" shall mean, 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 on the date of determination, as reported in The Wall Street
Journal or such other source as the Board 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 of the closing bid and asked prices for the
Common Stock on the date of determination, as reported in The Wall Street
Journal or such other source as the Board deems reliable;

                                      -2-
<PAGE>   3
                               (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 Board; or

                               (iv) For purposes of the Offering Date of the
first Offering Period under the Plan, the Fair Market Value shall be the initial
price to the public as set forth in the final prospectus included within the
registration statement in Form S-1 filed with the Securities and Exchange
Commission for the initial public offering of the Company's Common Stock (the
"Registration Statement").

                  (m) "Offering Date" shall mean the first Trading Day of each
Offering Period.

                  (n) "Offering Periods" shall mean the periods of approximately
twenty-four (24) months during which an option granted pursuant to the Plan may
be exercised, commencing on the first Trading Day on or after May 1st and
November 1st of each year and terminating on the first Trading Day on or after
the May 1st and November 1st Offering Period commencement date approximately
twenty-four months later; provided, however, that the first Offering Period
under the Plan shall commence with the first Trading Day on or after the date on
which the Securities and Exchange Commission declares the Company's Registration
Statement effective and ending on the first Trading Day on or after the earlier
of (i) May 1st, 2003 or (ii) twenty-seven (27) months from the beginning of
the first Offering Period. The duration and timing of Offering Periods may be
changed pursuant to Section 4 of this Plan.

                  (o) "Plan" shall mean this 2001 Employee Stock Purchase Plan.

                  (p) "Purchase Period" shall mean the approximately six (6)
month period commencing on one Exercise Date and ending with the next Exercise
Date, except that the first Purchase Period of any Offering Period shall
commence on the Offering Date and end with the next Exercise Date.

                  (q) "Purchase Price" shall mean 85% of the Fair Market Value
of a share of Common Stock on the Offering Date or on the Exercise Date,
whichever is lower; provided however, that the Purchase Price may be adjusted by
the Administrator pursuant to Section 20.

                  (r) "Subsidiary" shall mean a "subsidiary corporation,"
whether now or hereafter existing, as defined in Section 424(f) of the Code.

                  (s) "Trading Day" shall mean a day on which national stock
exchanges and the Nasdaq System are open for trading.

         3. Eligibility.

                  (a) First Offering Period. Any individual who is an Eligible
Employee immediately prior to the first Offering Period shall be automatically
enrolled in the first Offering Period.

                  (b) Subsequent Offering Periods. Any Eligible Employee on a
given Offering Date shall be eligible to participate in the Plan.

                                      -3-
<PAGE>   4
                  (c) Limitations. Any provisions of the Plan to the contrary
notwithstanding, no Eligible Employee shall be granted an option under the Plan
(i) to the extent that, immediately after the grant, such Eligible Employee (or
any other person whose stock would be attributed to such Eligible Employee
pursuant to Section 424(d) of the Code) would own capital stock of the Company
and/or hold outstanding options to purchase such stock possessing five percent
(5%) or more of the total combined voting power or value of all classes of the
capital stock of the Company or of any Subsidiary, or (ii) to the extent that
his or her rights to purchase stock under all employee stock purchase plans of
the Company and its subsidiaries accrues at a rate which exceeds Twenty-Five
Thousand Dollars ($25,000) worth of stock (determined at the fair market value
of the shares at the time such option is granted) for each calendar year in
which such option is outstanding at any time.

         4. Offering Periods. The Plan shall be implemented by consecutive,
overlapping Offering Periods with a new Offering Period commencing on the first
Trading Day on or after May 1st and November 1st each year, or on such other
date as the Board shall determine, and continuing thereafter until terminated in
accordance with Section 20 hereof; provided, however, that the first Offering
Period under the Plan shall commence with the first Trading Day on or after the
date on which the Securities and Exchange Commission declares the Company's
Registration Statement effective and ending on the first Trading Day on or after
the earlier of (i) May 1st, 2003 or (ii) twenty-seven (27) months from the
beginning of the first Offering Period. The Board shall have the power to change
the duration of Offering Periods (including the commencement dates thereof) with
respect to future offerings without stockholder approval if such change is
announced prior to the scheduled beginning of the first Offering Period to be
affected thereafter.

         5. Participation.

                  (a) First Offering Period. An Eligible Employee shall be
entitled to participate in the first Offering Period only if such individual
submits a subscription agreement authorizing payroll deductions in the form of
Exhibit A to this Plan (i) no earlier than the effective date of the Form S-8
registration statement with respect to the issuance of Common Stock under this
Plan and (ii) no later than five (5) business days from the effective date of
such S-8 registration statement (the "Enrollment Window"). An Eligible
Employee's failure to submit the subscription agreement during the Enrollment
Window shall result in the automatic termination of such individual's
participation in the Offering Period.

                  (b) Subsequent Offering Periods. An Eligible Employee may
become a participant in the Plan by completing a subscription agreement
authorizing payroll deductions in the form of Exhibit A to this Plan and filing
it with the Company's payroll office prior to the applicable Offering Date.

         6. Payroll Deductions.

                  (a) At the time a participant files his or her subscription
agreement, he or she shall elect to have payroll deductions made on each pay day
during the Offering Period in an amount not exceeding 15% of the Compensation
which he or she receives on each pay day during the Offering Period; provided,
however, that should a pay day occur on an Exercise Date, a participant shall
have the payroll deductions made on such day applied to his or her account under
the new

                                      -4-
<PAGE>   5
Offering Period or Purchase Period, as the case may be. A participant's
subscription agreement shall remain in effect for successive Offering Periods
unless terminated as provided in Section 10 hereof.

                  (b) Payroll deductions for a participant shall commence on the
first payday following the Offering Date and shall end on the last payday in the
Offering Period to which such authorization is applicable, unless sooner
terminated by the participant as provided in Section 10 hereof; provided,
however, that for the first Offering Period, payroll deductions shall commence
on the first payday on or following the end of the Enrollment Window.

                  (c) All payroll deductions made for a participant shall be
credited to his or her account under the Plan and shall be withheld in whole
percentages only. A participant may not make any additional payments into such
account.

                  (d) A participant may discontinue his or her participation in
the Plan as provided in Section 10 hereof, or may increase or decrease the rate
of his or her payroll deductions during the Offering Period by completing or
filing with the Company a new subscription agreement authorizing a change in
payroll deduction rate. The Administrator may, in its discretion, limit the
nature and/or number of participation rate changes during any Offering Period.
The change in rate shall be effective with the first full payroll period
following five (5) business days after the Company's receipt of the new
subscription agreement unless the Company elects to process a given change in
participation more quickly.

                  (e) Notwithstanding the foregoing, to the extent necessary to
comply with Section 423(b)(8) of the Code and Section 3(b) hereof, a
participant's payroll deductions may be decreased to zero percent (0%) at any
time during a Purchase Period. Payroll deductions shall recommence at the rate
provided in such participant's subscription agreement at the beginning of the
first Purchase Period which is scheduled to end in the following calendar year,
unless terminated by the participant as provided in Section 10 hereof.

                  (f) At the time the option is exercised, in whole or in part,
or at the time some or all of the Company's Common Stock issued under the Plan
is disposed of, the participant must make adequate provision for the Company's
federal, state, or other tax withholding obligations, if any, which arise upon
the exercise of the option or the disposition of the Common Stock. At any time,
the Company may, but shall not be obligated to, withhold from the participant's
compensation the amount necessary for the Company to meet applicable withholding
obligations, including any withholding required to make available to the Company
any tax deductions or benefits attributable to sale or early disposition of
Common Stock by the Eligible Employee.

         7. Grant of Option. On the Offering Date of each Offering Period, each
Eligible Employee participating in such Offering Period shall be granted an
option to purchase on each Exercise Date during such Offering Period (at the
applicable Purchase Price) up to a number of shares of the Company's Common
Stock determined by dividing such Eligible Employee's payroll deductions
accumulated prior to such Exercise Date and retained in the Participant's
account as of the Exercise Date by the applicable Purchase Price; provided that
in no event shall an Eligible Employee be permitted to purchase during each
Purchase Period more than 5,000 shares of the Company's Common Stock (subject to
any adjustment pursuant to Section 19), and provided further that such purchase
shall be subject to the limitations set forth in Sections 3(b) and 12 hereof.
The

                                      -5-
<PAGE>   6
Eligible Employee may accept the grant of such option by turning in a completed
Subscription Agreement (attached hereto as Exhibit A) to the Company on or prior
to an Offering Date, or with respect to the first Offering Period, prior to the
last day of the Enrollment Window. The Administrator may, for future Offering
Periods, increase or decrease, in its absolute discretion, the maximum number of
shares of the Company's Common Stock an Eligible Employee may purchase during
each Purchase Period of such Offering Period. Exercise of the option shall occur
as provided in Section 8 hereof, unless the participant has withdrawn pursuant
to Section 10 hereof. The option shall expire on the last day of the Offering
Period.

         8. Exercise of Option.

                  (a) Unless a participant withdraws from the Plan as provided
in Section 10 hereof, his or her option for the purchase of shares shall be
exercised automatically on the Exercise Date, and the maximum number of full
shares subject to option shall be purchased for such participant at the
applicable Purchase Price with the accumulated payroll deductions in his or her
account. No fractional shares shall be purchased; any payroll deductions
accumulated in a participant's account which are not sufficient to purchase a
full share shall be retained in the participant's account for the subsequent
Purchase Period or Offering Period, subject to earlier withdrawal by the
participant as provided in Section 10 hereof. Any other funds left over in a
participant's account after the Exercise Date shall be returned to the
participant. During a participant's lifetime, a participant's option to purchase
shares hereunder is exercisable only by him or her.

                  (b) If the Administrator determines that, on a given Exercise
Date, the number of shares with respect to which options are to be exercised may
exceed (i) the number of shares of Common Stock that were available for sale
under the Plan on the Offering Date of the applicable Offering Period, or (ii)
the number of shares available for sale under the Plan on such Exercise Date,
the Administrator may in its sole discretion (x) provide that the Company shall
make a pro rata allocation of the shares of Common Stock available for purchase
on such Offering Date or Exercise Date, as applicable, in as uniform a manner as
shall be practicable and as it shall determine in its sole discretion to be
equitable among all participants exercising options to purchase Common Stock on
such Exercise Date, and continue all Offering Periods then in effect, or (y)
provide that the Company shall make a pro rata allocation of the shares
available for purchase on such Offering Date or Exercise Date, as applicable, in
as uniform a manner as shall be practicable and as it shall determine in its
sole discretion to be equitable among all participants exercising options to
purchase Common Stock on such Exercise Date, and terminate any or all Offering
Periods then in effect pursuant to Section 20 hereof. The Company may make pro
rata allocation of the shares available on the Offering Date of any applicable
Offering Period pursuant to the preceding sentence, notwithstanding any
authorization of additional shares for issuance under the Plan by the Company's
stockholders subsequent to such Offering Date.

         9. Delivery. As soon as reasonably practicable after each Exercise Date
on which a purchase of shares occurs, the Company shall arrange the delivery to
each participant the shares purchased upon exercise of his or her option in a
form determined by the Administrator.

                                      -6-
<PAGE>   7
         10. Withdrawal.

                  (a) A participant may withdraw all but not less than all the
payroll deductions credited to his or her account and not yet used to exercise
his or her option under the Plan at any time by giving written notice to the
Company in the form of Exhibit B to this Plan. All of the participant's payroll
deductions credited to his or her account shall be paid to such participant
promptly after receipt of notice of withdrawal and such participant's option for
the Offering Period shall be automatically terminated, and no further payroll
deductions for the purchase of shares shall be made for such Offering Period. If
a participant withdraws from an Offering Period, payroll deductions shall not
resume at the beginning of the succeeding Offering Period unless the participant
delivers to the Company a new subscription agreement.

                  (b) A participant's withdrawal from an Offering Period shall
not have any effect upon his or her eligibility to participate in any similar
plan which may hereafter be adopted by the Company or in succeeding Offering
Periods which commence after the termination of the Offering Period from which
the participant withdraws.

         11. Termination of Employment. In the event a participant ceases to be
an Eligible Employee of the Company or any Designated Subsidiary, as applicable,
his or her option shall remain exercisable for a period of three (3) months from
the date of such Eligible Employee's termination. Upon the expiration of such
three (3) month period or a date prior to the expiration of such three (3) month
period if requested by the participant, any payroll deductions credited to such
participant's account during the Offering Period but not yet used to purchase
shares under the Plan shall be returned to such participant or, in the case of
his or her death, to the person or persons entitled thereto under Section 15
hereof, and such participant's option shall be automatically terminated.

         12. Interest. No interest shall accrue on the payroll deductions of a
participant in the Plan.

         13. Stock.

                  (a) Subject to adjustment upon changes in capitalization of
the Company as provided in Section 19 hereof, the maximum number of shares of
the Company's Common Stock which shall be made available for sale under the Plan
shall be 250,000 shares plus an annual increase to be added on the first day of
the Company's fiscal year beginning in 2002, equal to the lesser of (i) 800,000
shares, (ii) 2% of the outstanding shares on such date or (iii) an amount
determined by the Administrator.

                  (b) 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), a participant shall only have the rights of an unsecured
creditor with respect to such shares, and no right to vote or receive dividends
or any other rights as a stockholder shall exist with respect to such shares.

                  (c) Shares to be delivered to a participant under the Plan
shall be registered in the name of the participant or in the name of the
participant and his or her spouse.

                                      -7-
<PAGE>   8
         14. Administration. The Administrator shall administer the Plan and
shall have full and exclusive discretionary authority to construe, interpret and
apply the terms of the Plan, to determine eligibility and to adjudicate all
disputed claims filed under the Plan. Every finding, decision and determination
made by the Administrator shall, to the full extent permitted by law, be final
and binding upon all parties.

         15. Designation of Beneficiary.

                  (a) A participant may file a written designation of a
beneficiary who is to receive any shares and cash, if any, from the
participant's account under the Plan in the event of such participant's death
subsequent to an Exercise Date on which the option is exercised but prior to
delivery to such participant of such shares and cash. In addition, a participant
may file a written designation of a beneficiary who is to receive any cash from
the participant's account under the Plan in the event of such participant's
death prior to exercise of the option. If a participant is married and the
designated beneficiary is not the spouse, spousal consent shall be required for
such designation to be effective.

                  (b) Such designation of beneficiary may be changed by the
participant at any time by written notice. In the event of the death of a
participant and in the absence of a beneficiary validly designated under the
Plan who is living at the time of such participant's death, the Company shall
deliver such shares and/or cash to the executor or administrator of the estate
of the participant, or if no such executor or administrator has been appointed
(to the knowledge of the Company), the Company, in its discretion, may deliver
such shares and/or cash to the spouse or to any one or more dependents or
relatives of the participant, or if no spouse, dependent or relative is known to
the Company, then to such other person as the Company may designate.

                  (c) All beneficiary designations shall be in such form and
manner as the Administrator may designate from time to time.

         16. Transferability. Neither payroll deductions credited to a
participant's account nor any rights with regard to the exercise of an option or
to receive shares under the Plan may be assigned, transferred, pledged or
otherwise disposed of in any way (other than by will, the laws of descent and
distribution or as provided in Section 15 hereof) by the participant. Any such
attempt at assignment, transfer, pledge or other disposition shall be without
effect, except that the Company may treat such act as an election to withdraw
funds from an Offering Period in accordance with Section 10 hereof.

         17. Use of Funds. All payroll deductions received or held by the
Company under the Plan may be used by the Company for any corporate purpose, and
the Company shall not be obligated to segregate such payroll deductions. Until
shares are issued, participants shall only have the rights of an unsecured
creditor.

         18. Reports. Individual accounts shall be maintained for each
participant in the Plan. Statements of account shall be given to participating
Eligible Employees at least annually, which statements shall set forth the
amounts of payroll deductions, the Purchase Price, the number of shares
purchased and the remaining cash balance, if any.

                                      -8-
<PAGE>   9
         19. Adjustments Upon Changes in Capitalization, Dissolution,
Liquidation, Merger or Change of Control.

                  (a) Changes in Capitalization. Subject to any required action
by the stockholders of the Company, the maximum number of shares of the
Company's Common Stock which shall be made available for sale under the Plan,
the maximum number of shares each participant may purchase each Purchase Period
(pursuant to Section 7), the number of shares that may be added annually to the
shares reserved under the Plan (pursuant to Section 13(a)(i)), as well as the
price per share and the number of shares of Common Stock covered by each option
under the Plan which has not yet been exercised shall be proportionately
adjusted for any increase or decrease in the 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 change in the
number of shares of Common Stock effected without receipt of consideration by
the Company; provided, however, that 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 Administrator, 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.

                  (b) Dissolution or Liquidation. In the event of the proposed
dissolution or liquidation of the Company, the Offering Period then in progress
shall be shortened by setting a new Exercise Date (the "New Exercise Date"), and
shall terminate immediately prior to the consummation of such proposed
dissolution or liquidation, unless provided otherwise by the Administrator. The
New Exercise Date shall be before the date of the Company's proposed dissolution
or liquidation. The Administrator shall notify each participant in writing, at
least ten (10) business days prior to the New Exercise Date, that the Exercise
Date for the participant's option has been changed to the New Exercise Date and
that the participant's option shall be exercised automatically on the New
Exercise Date, unless prior to such date the participant has withdrawn from the
Offering Period as provided in Section 10 hereof.

                  (c) Merger or Change of Control. In the event of a merger or
Change of Control, each outstanding option shall be assumed or an equivalent
option 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, any Purchase Periods then in progress shall
be shortened by setting a New Exercise Date and any Offering Periods then in
progress shall end on the New Exercise Date. The New Exercise Date shall be
before the date of the Company's proposed merger or Change of Control. The
Administrator shall notify each participant in writing, at least ten (10)
business days prior to the New Exercise Date, that the Exercise Date for the
participant's option has been changed to the New Exercise Date and that the
participant's option shall be exercised automatically on the New Exercise Date,
unless prior to such date the participant has withdrawn from the Offering Period
as provided in Section 10 hereof.

                                      -9-
<PAGE>   10
         20. Amendment or Termination.

                  (a) The Administrator may at any time and for any reason
terminate or amend the Plan. Except as otherwise provided in the Plan, no such
termination can affect options previously granted, provided that an Offering
Period may be terminated by the Administrator on any Exercise Date if the
Administrator determines that the termination of the Offering Period or the Plan
is in the best interests of the Company and its stockholders. Except as provided
in Section 19 and this Section 20 hereof, no amendment may make any change in
any option theretofore granted which adversely affects the rights of any
participant. To the extent necessary to comply with Section 423 of the Code (or
any successor rule or provision or any other applicable law, regulation or stock
exchange rule), the Company shall obtain stockholder approval in such a manner
and to such a degree as required.

                  (b) Without stockholder consent and without regard to whether
any participant rights may be considered to have been "adversely affected," the
Administrator shall be entitled to change the Offering Periods, limit the
frequency and/or number of changes in the amount withheld during an Offering
Period, establish the exchange ratio applicable to amounts withheld in a
currency other than U.S. dollars, permit payroll withholding in excess of the
amount designated by a participant in order to adjust for delays or mistakes in
the Company's processing of properly completed withholding elections, establish
reasonable waiting and adjustment periods and/or accounting and crediting
procedures to ensure that amounts applied toward the purchase of Common Stock
for each participant properly correspond with amounts withheld from the
participant's Compensation, and establish such other limitations or procedures
as the Administrator determines in its sole discretion advisable which are
consistent with the Plan.

                  (c) In the event the Administrator determines that the ongoing
operation of the Plan may result in unfavorable financial accounting
consequences, the Board may, in its discretion and, to the extent necessary or
desirable, modify or amend the Plan to reduce or eliminate such accounting
consequence including, but not limited to:

                               (i) increasing the Purchase Price for any
Offering Period including an Offering Period underway at the time of the change
in Purchase Price;

                               (ii) shortening any Offering Period so that
Offering Period ends on a new Exercise Date, including an Offering Period
underway at the time of the Board action; and

                               (iii) allocating shares.

Such modifications or amendments shall not require stockholder approval or the
consent of any Plan participants.

         21. Notices. All notices or other communications by a participant to
the Company under or in connection with the Plan shall be deemed to have been
duly given when received in the form and manner specified by the Company at the
location, or by the person, designated by the Company for the receipt thereof.

                                      -10-
<PAGE>   11
         22. Conditions Upon Issuance of Shares. Shares shall not be issued with
respect to an option unless the exercise of such option and the issuance and
delivery of such shares pursuant thereto shall comply with all applicable
provisions of law, domestic or foreign, including, without limitation, the
Securities Act of 1933, as amended, the Securities Exchange Act of 1934, as
amended, the rules and regulations promulgated thereunder, and the requirements
of any stock exchange upon which the shares may then be listed, and shall be
further subject to the approval of counsel for the Company with respect to such
compliance.

         As a condition to the exercise of an option, the Company 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 by any of
the aforementioned applicable provisions of law.

         23. Term of Plan. The Plan shall become effective upon the earlier to
occur of its adoption by the Board of Directors or its approval by the
stockholders of the Company. It shall continue in effect until terminated under
Section 20 hereof.

         24. Automatic Transfer to Low Price Offering Period. To the extent
permitted by any applicable laws, regulations, or stock exchange rules if the
Fair Market Value of the Common Stock on any Exercise Date in an Offering Period
is lower than the Fair Market Value of the Common Stock on the Offering Date of
such Offering Period, then all participants in such Offering Period shall be
automatically withdrawn from such Offering Period immediately after the exercise
of their option on such Exercise Date and automatically re-enrolled in the
immediately following Offering Period.

                                      -11-
<PAGE>   12
                                    EXHIBIT A

                             SIMPLEX SOLUTIONS, INC.

                        2001 EMPLOYEE STOCK PURCHASE PLAN

                             SUBSCRIPTION AGREEMENT

_____ Original Application                            Offering Date:___________
_____ Change in Payroll Deduction Rate
_____ Change of Beneficiary(ies)

1.       ____________________ hereby elects to participate in the Simplex
         Solutions, Inc. 2001 Employee Stock Purchase Plan (the "Employee Stock
         Purchase Plan") and subscribes to purchase shares of the Company's
         Common Stock in accordance with this Subscription Agreement and the
         Employee Stock Purchase Plan.

2.       I hereby authorize payroll deductions from each paycheck in the amount
         of ____% of my Compensation on each payday (from 0 to 15%) during the
         Offering Period in accordance with the Employee Stock Purchase Plan.
         (Please note that no fractional percentages are permitted.)

3.       I understand that said payroll deductions shall be accumulated for the
         purchase of shares of Common Stock at the applicable Purchase Price
         determined in accordance with the Employee Stock Purchase Plan. I
         understand that if I do not withdraw from an Offering Period, any
         accumulated payroll deductions will be used to automatically exercise
         my option.

4.       I have received a copy of the complete Employee Stock Purchase Plan. I
         understand that my participation in the Employee Stock Purchase Plan is
         in all respects subject to the terms of the Plan. I understand that my
         ability to exercise the option under this Subscription Agreement is
         subject to stockholder approval of the Employee Stock Purchase Plan.

5.       Shares purchased for me under the Employee Stock Purchase Plan should
         be issued in the name(s) of (Eligible Employee or Eligible Employee and
         Spouse only).

6.       I understand that if I dispose of any shares received by me pursuant to
         the Plan within 2 years after the Offering Date (the first day of the
         Offering Period during which I purchased such shares) or one year after
         the Exercise Date, I will be treated for federal income tax purposes as
         having received ordinary income at the time of such disposition in an
         amount equal to the excess of the fair market value of the shares at
         the time such shares were purchased by me over the price which I paid
         for the shares. I hereby agree to notify the Company in writing within
         30 days after the date of any disposition of my shares and I will make
         adequate provision for Federal, state or other tax withholding
         obligations, if any, which arise upon the

<PAGE>   13
         disposition of the Common Stock. The Company may, but will not be
         obligated to, withhold from my compensation the amount necessary to
         meet any applicable withholding obligation including any withholding
         necessary to make available to the Company any tax deductions or
         benefits attributable to sale or early disposition of Common Stock by
         me. If I dispose of such shares at any time after the expiration of the
         2-year and 1-year holding periods, I understand that I will be treated
         for federal income tax purposes as having received income only at the
         time of such disposition, and that such income will be taxed as
         ordinary income only to the extent of an amount equal to the lesser of
         (1) the excess of the fair market value of the shares at the time of
         such disposition over the purchase price which I paid for the shares,
         or (2) 15% of the fair market value of the shares on the first day of
         the Offering Period. The remainder of the gain, if any, recognized on
         such disposition will be taxed as capital gain.

7.       I hereby agree to be bound by the terms of the Employee Stock Purchase
         Plan. The effectiveness of this Subscription Agreement is dependent
         upon my eligibility to participate in the Employee Stock Purchase Plan.

8.       In the event of my death, I hereby designate the following as my
         beneficiary(ies) to receive all payments and shares due me under the
         Employee Stock Purchase Plan:

         NAME:  (Please print)__________________________________________________
                               (First)             (Middle)            (Last)

         _________________________     _________________________________________
         Relationship

         _________________________     _________________________________________
         Percentage Benefit                          (Address)

         NAME: (please print)
         _______________________________________________________________________
                               (First)              (Middle)           (Last)

         _________________________     _________________________________________
         Relationship

         _________________________     _________________________________________
         Percentage of Benefit                       (Address)

                                       -2-
<PAGE>   14
         Employee's Social
         Security Number:                   ____________________________________

         Employee's Address:                ____________________________________

                                            ____________________________________

                                            ____________________________________

I UNDERSTAND THAT THIS SUBSCRIPTION AGREEMENT SHALL REMAIN IN EFFECT THROUGHOUT
SUCCESSIVE OFFERING PERIODS UNLESS TERMINATED BY ME.

Dated:_________________________        _________________________________________
                                       Signature of Employee

                                       _________________________________________
                                       Spouse's Signature (If beneficiary other
                                       than spouse)

                                       -3-
<PAGE>   15
                                    EXHIBIT B

                             SIMPLEX SOLUTIONS, INC.

                        2001 EMPLOYEE STOCK PURCHASE PLAN

                              NOTICE OF WITHDRAWAL

         The undersigned participant in the Offering Period of the Simplex
Solutions, Inc. 2001 Employee Stock Purchase Plan which began on ____________,
______ (the "Offering Date") hereby notifies the Company that he or she hereby
withdraws from the Offering Period. He or she hereby directs the Company to pay
to the undersigned as promptly as practicable all the payroll deductions
credited to his or her account with respect to such Offering Period. The
undersigned understands and agrees that his or her option for such Offering
Period will be automatically terminated. The undersigned understands further
that no further payroll deductions will be made for the purchase of shares in
the current Offering Period and the undersigned shall be eligible to participate
in succeeding Offering Periods only by delivering to the Company a new
Subscription Agreement.

                                       Name and Address of Participant:

                                       ________________________________________

                                       ________________________________________

                                       ________________________________________

                                       Signature:

                                       ________________________________________

                                       Date:___________________________________

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