EXHIBIT 10.18
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This  Debenture has not been  registered  under the  Securities  Act of 1933, as
amended ("Act"),  or applicable state securities laws ("State Acts"),  and shall
not be sold,  hypothecated,  or otherwise  transferred,  unless such transfer is
made in compliance with the Act and the State Acts.
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                               SIMTEK CORPORATION



                           7.50% CONVERTIBLE DEBENTURE


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$1,000,000                                                                 No. 2
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                          Date of Issue: June 28, 2002

         SIMTEK   CORPORATION,   a  Colorado   corporation   (the  "Company"  or
"Borrower"), for value received, promises to pay to:

                     The Frost National Bank, Custodian FBO
               RENAISSANCE CAPITAL GROWTH & INCOME FUND III, INC.
                               TRUST NO. W00740000

or to its order, (together with any assignee, jointly or severally, the "Holder"
or "Lender") on or before June 28, 2009 (the "Due Date")  (unless this Debenture
shall have been sooner  called for  redemption  or presented  for  conversion as
herein provided),  the sum of One Million Dolllars  ($1,000,000) (the "Principal
Amount") and to pay interest on the unpaid Principal Amount at the rate of 7.50%
per annum.  All payments of both  principal  and  interest  shall be made at the
address  of the  Holder  hereof as it  appears  in the books and  records of the
Borrower, or at such other place as may be designated by the Holder hereof.

     1. INTEREST. Interest on the Principal Amount outstanding from time to time
shall be  payable  in  monthly  installments  commencing  August  1,  2002,  and
subsequent  payments  shall be made on the  first day of each  month  thereafter
until the Principal  Amount and all accrued and unpaid  interest shall have been
paid in full.  Overdue  principal  and  interest  on the  Debenture  shall  bear
interest at the maximum rate permitted by applicable law.

     2.  MATURITY.  If not sooner paid,  redeemed or converted,  this  Debenture
shall  mature on June 28,  2009 at which  time the  remaining  unpaid  Principal
Amount, and all accrued and unpaid interest and any other charges then due under
the Convertible Loan Agreement, shall be due and payable in full. This Debenture
shall be prepaid pro rata with any prepayments of Indebtedness other than Senior
Obligations.  This  Debenture  shall be senior in right of  payment to all other
Indebtedness of the Company, except the Senior Obligations.


<PAGE>


     3.  MANDATORY  PRINCIPAL  INSTALLMENTS.  If this  Debenture  is not  sooner
redeemed or  converted  as  provided  hereunder,  Borrower  shall pay to Holder,
commencing on June 28, 2005 and  continuing on the first day of each  successive
month thereafter prior to maturity, mandatory principal redemption installments,
each of such  installments  to be in the  amount  of Ten  Dollars  ($10) per One
Thousand Dollars ($1,000) of the then remaining  Principal Amount,  and further,
at maturity,  Borrower shall pay to Holder a final  installment of the remaining
unpaid  Principal  Amount and all accrued and unpaid  interest on this Debenture
and any other  charges  then due under this  Debenture or the  Convertible  Loan
Agreement.

     4.  OPTIONAL REDEMPTION BY HOLDER.

         (a) If at any time  after  the date  hereof  (i) the  Company's  Common
Stock, par value $0.01 per share ("Common Stock"), is not listed on the New York
Stock Exchange  ("NYSE") or the American Stock Exchange  ("AMEX"),  or quoted on
the NASDAQ  National  Market System  ("National  Market") or the NASDAQ SmallCap
System ("SmallCap") or the Over-the-Counter Bulletin Board ("OTCBB"), (ii) there
is a change of control of the Company's voting  securities,  without the written
consent of the Holder,  (iii) there is a change of at least  two-thirds (2/3) of
the members of the  Company's  Board of  Directors as it shall exist on the date
hereof, without the written consent of the Holder, (iv) all or substantially all
of the assets or capital  stock of the  Company  or its  subsidiaries  are sold,
without the consent of the Holder,  or (v) the Company or its  subsidiaries  are
merged or consolidated with or into unaffiliated  entities,  without the written
consent of Holder,  the Holder shall have the right to require this Debenture to
be redeemed by the Company at the sum equal to the  Principal  Amount,  together
with an amount equal to an 18% annual yield on the Principal  Amount through the
date of redemption (the "Redemption Date").

         (b) The  Holder may  exercise  its right to  require  that the  Company
redeem  this  Debenture  pursuant  to Section  4(a) prior to  maturity by giving
notice  thereof  to the  Company,  which  notice  shall  specify  the  terms  of
redemption  (including  the place at which the Holder may obtain  payment),  the
total  redemption  payment and the Redemption Date, which date shall not be less
than 30 days nor more than 90 days after the date of the notice.

     5.  OPTIONAL REDEMPTION BY COMPANY.

         (a) On any interest  payment  date,  and after  receipt of  irrevocable
notice from the Borrower as provided for below, this Debenture is redeemable, in
whole but not in part,  at 101% of the Principal  Amount,  together with accrued
and unpaid interest through the Redemption  Date, by the Company,  if all of the
following  conditions are satisfied:  (i) the average  closing bid price for the
Common Stock for the twenty (20)  consecutive  trading days prior to the date of
notice exceeds an amount equal to three (3) times the  Conversion  Price then in
effect,  and the Common  Stock is listed or quoted on the National  Market,  the
SmallCap,  AMEX,  OTCBB or NYSE;  (ii) the average daily trading  volume for the
twenty (20) consecutive trading days prior to the date of the irrevocable notice
shall be no less than one hundred twenty-five  thousand (125,000) shares;  (iii)
the  market  price  for the  Common  Stock  at the  time of  notice  reflects  a
price-to-earnings  ratio of no greater than twenty-five (25) times fully diluted
earnings per share,  excluding any  extraordinary  gains; and (iv) the shares of


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<PAGE>


Common Stock issuable upon  conversion of this  Debenture  shall have been fully
registered under  applicable  securities laws. The Company's right of redemption
is subject to the Holder's prior right of conversion of the Debenture.

         (b) If the Holder  shall notify the Company in writing of its intent to
sell or  otherwise  transfer  the  Debenture  (other than to an  affiliate  or a
nominee  holder of record),  this  Debenture  is  redeemable  at the  Borrower's
option, in whole but not in part, at 101% of the Principle Amount, together with
accrued and unpaid  interest  through the Redemption  Date, by the Company for a
period of up to thirty (30) days after the date of notice.

         (c) The  Company  may  exercise  its  right to  redeem  this  Debenture
pursuant to Sections 5(a) and (b) prior to maturity by giving notice  thereof to
the Holder of this  Debenture as such name appears on the books of the Borrower,
which notice shall specify the terms of redemption (including the place at which
the Holder may obtain payment),  the total redemption payment and the Redemption
Date,  which date shall not be less than 30 days nor more than 90 days after the
date of the notice.

     6. CONVERSION  RIGHT. The Holder of this Debenture shall have the right, at
Holder's option, at any time, to convert all, or, in multiples of $100,000,  any
part of this Debenture into such number of fully paid and  nonassessable  shares
of Common Stock as provided  herein.  The Holder of this  Debenture may exercise
the  conversion  right by giving  written  notice (the  "Conversion  Notice") to
Borrower  of the  exercise  of such right and stating the name or names in which
the stock  certificate or stock  certificates for the shares of Common Stock are
to be issued and the address to which such certificates shall be delivered.  The
Conversion Notice shall be accompanied by the Debenture. The number of shares of
Common Stock that shall be issuable upon conversion of the Debenture shall equal
the  outstanding  Principal  Amount of the Debenture  divided by the  Conversion
Price (as  defined  below)  and in effect on the date the  Conversion  Notice is
given; provided,  however, that in the event that this Debenture shall have been
partially redeemed,  shares of Common Stock shall be issued pro rata, rounded to
the nearest whole share. Conversion shall be deemed to have been effected on the
date the Conversion  Notice is received (the "Conversion  Date"). In the case of
any Debenture  called for redemption,  the conversion  rights will expire at the
close of business on the Redemption Date. Within twenty (20) business days after
receipt of the  Conversion  Notice,  Borrower  shall  issue and  deliver by hand
against a signed receipt therefor or by United States  registered  mail,  return
receipt  requested,  to the address designated in the Conversion Notice, a stock
certificate or stock certificates of Borrower  representing the number of shares
of Common  Stock to which  Holder is entitled  and a check or cash in payment of
all  interest  accrued  and  unpaid on the  Debenture  up to and  including  the
Conversion  Date.  The  conversion  rights  will be  governed  by the  following
provisions:

         (a) CONVERSION  PRICE.  On the issue date hereof and until such time as
an adjustment shall occur, the initial Conversion Price shall be $.312.

         (b)  ADJUSTMENT  FOR  ISSUANCE  OF SHARES  AT LESS THAN THE  CONVERSION
PRICE.  If and whenever any Additional  Common Stock shall be issued by Borrower
(the "Stock Issue Date") for a consideration  per share less than the Conversion
Price, then in each such case the initial Conversion Price shall be reduced to a


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<PAGE>


new  Conversion  Price  in an  amount  equal  to the  price  per  share  for the
Additional  Common Stock then  issued,  if issued in  connection  with a sale of
shares,  or the value of the Additional  Common Stock then issued, as determined
in accordance with generally  accepted  accounting  principles,  if issued other
than for cash, and the number of shares issuable to Holder upon conversion shall
be proportionately increased; and, in the case of Additional Common Stock issued
without  consideration,  the initial Conversion Price shall be reduced in amount
and the number of shares issued upon conversion  shall be increased in an amount
so as to maintain for the Holder the right to convert the Debenture  into shares
equal in amount  to the same  percentage  interest  in the  Common  Stock of the
Company as existed for the Holder immediately preceding the Stock Issue Date.

         (c) SALE OF SHARES.  In case of the issuance of Additional Common Stock
for a  consideration  part or all of which shall be cash, the amount of the cash
consideration  therefor  shall be deemed to be the gross amount of the cash paid
to Borrower for such shares,  before deducting any underwriting  compensation or
discount  in the sale,  underwriting  or  purchase  thereof by  underwriters  or
dealers or others  performing  similar services or for any expenses  incurred in
connection therewith. In case of the issuance of any shares of Additional Common
Stock for a  consideration  part or all of which  shall be other than cash,  the
amount of the consideration therefor, other than cash, shall be deemed to be the
then fair market value of the property received.

         (d) STOCK SPLITS, SUBDIVISIONS OR COMBINATIONS. In the event of a stock
split or  subdivision of shares of Common Stock into a greater number of shares,
the Conversion Price shall be proportionately  decreased,  and in the event of a
combination  of shares of Common  Stock  into a smaller  number of  shares,  the
Conversion Price shall be proportionately  increased, such increase or decrease,
as the case may be, becoming effective at the record date.

         (e) STOCK  DIVIDENDS.  Shares of Common  Stock  issued as a dividend or
other  distribution on any class of capital stock of Borrower shall be deemed to
have been issued without consideration.

         (f) EXCEPTIONS.  The term  "Additional  Common Stock" herein shall mean
all shares of Common Stock or securities  convertible or exercisable into shares
of Common Stock hereafter issued by Borrower (including Common Stock held in the
treasury of Borrower), except (A) Common Stock issued upon the conversion of any
of the  Debentures;  (B)  Common  Stock  issuable  upon  exercise  of  presently
outstanding amounts or stock options; or (C) up to one million two hundred fifty
thousand  (1,250,000)  shares of Common Stock issuable upon exercise of employee
stock  options to be granted in the future at less than the  initial  Conversion
Price.

         (g)  ADJUSTMENT  FOR  MERGERS AND  CONSOLIDATIONS.  In the event of any
consolidation  or  merger  of the  Company  with or into,  or the sale of all or
substantially  all of the properties  and assets of the Company,  to any person,
and in connection therewith, consideration is payable to holders of Common Stock
in  cash,   securities  or  other   property,   then  as  a  condition  of  such
consolidation, merger or sale, lawful provision shall be made, and duly executed
documents  evidencing  the same shall be  delivered  to the Holder,  so that the
Holder shall have the right at any time prior to the maturity of this  Debenture
to purchase, at a total price equal to the Conversion Price immediately prior to
such event, the kind and amount of cash, securities or other property receivable


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<PAGE>


in connection with such  consolidation,  merger or sale, by a holder of the same
number of shares of Common Stock as were  convertible by the Holder  immediately
prior to such  consolidation,  merger  or sale.  In any such  case,  appropriate
provisions  shall be made with  respect to the rights and interest of the Holder
so that the provisions hereof shall thereafter be applicable with respect to any
cash,  securities or property deliverable upon exercise hereof.  Notwithstanding
the foregoing,  (i) if the Company merges or consolidates  with, or sells all or
substantially  all  of its  property  and  assets  to,  any  other  person,  and
consideration is payable to holders of Common Stock in exchange for their Common
Stock in  connection  with such  merger,  consolidation  or sale which  consists
solely of cash, or (ii) in the event of the dissolution,  liquidation or winding
up of the Company, then the Holder shall be entitled to receive distributions on
the date of such event on the same basis with holders of Common Stock as if this
Debenture  had  been  converted  immediately  prior  to  such  event,  less  the
Conversion Price. Upon receipt of such payment, if any, the rights of the Holder
shall terminate and cease and this Debenture  shall expire.  In case of any such
merger,  consolidation or sale of assets, the surviving or acquiring person and,
in the event of any dissolution,  liquidation or winding up of the Company,  the
Company  shall  promptly,  after  receipt of this  surrendered  Debenture,  make
payment by delivering a check in such amount as is appropriate  (or, in the case
of consideration other than cash, such other consideration as is appropriate) to
such  person as it may be directed  in writing by the Holder  surrendering  this
Debenture.

         (h)  DISTRIBUTIONS.  In the event of  distribution  to all Common Stock
holders  of any  securities,  cash or  properties  or assets or other  rights to
purchase securities or assets,  then, after such event, this debenture will also
be convertible  into the kind and amount of securities,  cash and other property
which the Holder  would have been  entitled  to receive if the Holder  owned the
Common Stock issuable upon conversion of the Debenture  immediately prior to the
occurrence of such event.

         (i) CAPITAL REORGANIZATION AND RECLASSIFICATION. In case of any capital
reorganization or reclassification of the Common Stock of Borrower (other than a
change in par value or as a result of a stock dividend, subdivision, split up or
combination of shares),  this Debenture  shall be convertible  into the kind and
number of shares of stock or other  securities  or property of Borrower to which
the Holder of the  Debenture  would have been  entitled to receive if the Holder
owned the Common Stock  issuable upon  conversion  of the Debenture  immediately
prior  to the  occurrence  of such  event.  The  provisions  of the  immediately
foregoing   sentence  shall  similarly  apply  to  successive   reorganizations,
reclassifications,   consolidations,   exchanges,  leases,  transfers  or  other
dispositions or other share exchanges.

         (j)  NOTICE.  In the event  Borrower  shall  propose to take any action
which shall result in an adjustment in the Conversion Price, Borrower shall give
notice to the Holder of this  Debenture,  which notice shall  specify the record
date,  if any,  with respect to such action and the date on which such action is
to take place.  Such  notice  shall be given on or before the earlier of 10 days
before the record date or the date which such action shall be taken. Such notice
shall also set forth all facts (to the extent  known)  material to the effect of
such action on the Conversion  Price and the number,  kind or class of shares or
other  securities or property which shall be deliverable or purchasable upon the
occurrence of such action or deliverable upon conversion of this Debenture.

         (k) CERTIFICATE.  Following  completion of an event which results in an
adjustment to the Conversion Price, Borrower shall furnish to the Holder of this
Debenture a statement,  signed by the Chief Executive  Officer and the Secretary
of the  Borrower,  of the facts  creating such  adjustment  and  specifying  the
resultant  adjusted  Conversion  Price then in  effect,  which  statement  shall
constitute an amendment to this Debenture.

         (l)  VOTE  OF  SHAREHOLDERS.  In  the  event  of an  adjustment  to the
Conversion  Price  due  to a  sale  of  securities  by the  Borrower  below  the
Conversion Price which would result in the Holders of all Debentures  evidencing
the Loan  having  the right to  acquire  more  than 20% of the then  outstanding
shares of Common Stock,  the Borrower agrees to hold a vote of the  shareholders
within 120 days of such event to authorize such an adjustment.  In the event the
shareholders do not authorize the issuance of such additional shares within such
period,  the  Holder  shall  have the right to cause the  Company  to redeem the
Debenture in accordance with the provisions of Section 4.


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<PAGE>


     7. RESERVATION OF SHARES. Borrower warrants and agrees that it shall at all
times  reserve  and keep  available,  free from  preemptive  rights,  sufficient
authorized  and  unissued  shares of Common  Stock or treasury  shares of Common
Stock necessary to effect conversion of this Debenture.

     8. TAXES.  The Company  shall pay any  documentary  or other  transactional
taxes  attributable  to the issuance or delivery of this Debenture or the shares
of Common Stock issued upon  conversion  by the Holder  (excluding  any federal,
state or local income taxes and any  franchise  taxes or taxes  imposed upon the
Holder by the jurisdiction,  or any political  subdivision thereof,  under which
such Holder is organized or is qualified to do business).

     9.  DEFAULT.

         (a) EVENT OF DEFAULT. An "Event of Default" shall exist if an "Event of
Default" (as defined in that certain Convertible Loan Agreement, dated, June 28,
2002,  among  Borrower,  Lenders and  Renaissance  Capital Group,  Inc., a Texas
corporation,  as  agent  for the  Lenders  (the  "Agent"))  shall  occur  and be
continuing.

         (b) REMEDIES  UPON EVENT OF DEFAULT.  If an Event of Default shall have
occurred and be continuing,  then the Holder may exercise any one or more of the
rights and remedies  provided in the Loan Documents,  as the Holder, in its sole
discretion, may deem necessary or appropriate.

         (c) REMEDIES  NONEXCLUSIVE.  Each right,  power or remedy of the Holder
hereof  upon the  occurrence  of any Event of  Default as  provided  for in this
Debenture or now or hereafter  existing at law or in equity or by statute  shall
be  cumulative  and  concurrent  and shall be in addition to every other  right,
power or remedy  provided for in this Debenture or now or hereafter  existing at
law or in equity or by statute, and the exercise or beginning of the exercise by
the Holder or  transferee  hereof of any one or more of such  rights,  powers or
remedies shall not preclude the  simultaneous or later exercise by the Holder of
any or all such other rights, powers or remedies.


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<PAGE>


         (d) EXPENSES.  Upon the occurrence of a Default or an Event of Default,
which  occurrence  is not cured  within the notice  provisions,  if any provided
therefore,  Borrower  agrees  to pay and  shall  pay all  reasonable  costs  and
expenses  (including  attorneys'  fees and  expenses)  incurred by the Holder in
connection  with the  preservation  and enforcement of Holder's rights under the
Convertible Loan Agreement, the Debenture, or any other Loan Document.

     10. FAILURE TO ACT AND WAIVER.  No failure or delay by the Holder hereof to
require  the  performance  of any  term or  terms  of this  Debenture  or not to
exercise any right or any remedy  shall  constitute a waiver of any such term or
of any right or of any  default,  nor shall such delay or failure  preclude  the
Holder hereof from exercising any such right,  power or remedy at any later time
or times.  By accepting  payment after the due date of any amount  payable under
this Debenture,  the Holder hereof shall not be deemed to waive the right either
to require payment when due of all other amounts payable,  or to later declare a
default for failure to effect such payment of any such other amount. The failure
of the Holder of this  Debenture  to give notice of any failure or breach of the
Borrower  under this  Debenture  shall not  constitute  a waiver of any right or
remedy in respect of such continuing failure or breach or any subsequent failure
or breach.

     11.  CONSENT TO  JURISDICTION.  The Company hereby agrees and consents that
any action, suit or proceeding arising out of this Debenture shall be brought in
any state or federal court in Dallas County, Texas,  including the United States
District Court for the Northern  District of Texas,  all at the sole election of
the Holder  hereof,  and by the issuance and  execution of this  Debenture,  the
Borrower  irrevocably  consents to the exclusive  jurisdiction and venue of each
such court.  The Company  hereby  irrevocably  appoints CT  Corporation  System,
Dallas, Texas, as agent for the Borrower to accept service of process for and on
behalf of the  Borrower in any action,  suit or  proceeding  arising out of this
Debenture.  Except for default in payment of interest or  principal  when and as
they  become  due,  and except as  otherwise  specifically  set forth  herein or
otherwise  agreed to in writing by the parties,  any action,  dispute,  claim or
controversy (all such herein called  "Dispute")  between or among the parties as
to the  facts  or the  interpretation  of the  Debenture  shall be  resolved  by
arbitration as set forth in the Convertible Loan Agreement.

     12. HOLDER'S RIGHT TO REQUEST MULTIPLE  DEBENTURES.  The Holder shall, upon
written  request  and  presentation  of the  Debenture,  have the right,  at any
interest  payment  date,  to request  division of this  Debenture  into multiple
instruments, each of such to be in such amounts as shall be requested; provided,
however,  that no  Debenture  shall be  issued  in  denominations  of less  than
$50,000.

     13.  TRANSFER.  Subject to Section 12.08 of the Convertible Loan Agreement,
this Debenture may be transferred on the books of the Borrower by the registered
Holder hereof, or by Holder's attorney duly authorized in writing,  in multiples
of  $100,000,  only  upon  (i)  delivery  to the  Borrower  of a  duly  executed
assignment of the Debenture,  or part thereof, to the proposed new Holder, along
with a current  notation of the amount of payments  received  and net  Principal
Amount yet unfunded, and presentment of such Debenture to the Borrower for issue
of a replacement Debenture,  or Debentures,  in the name of the new Holder, (ii)


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<PAGE>


the  designation by the new Holder of the Lender's agent for notice,  such agent
to be the sole party to whom Borrower  shall be required to provide  notice when
notice  to  Holder  is  required  hereunder  and who  shall  be the  sole  party
authorized to represent  Lender in regard to  modification  or waivers under the
Debenture,  the  Convertible  Loan Agreement,  or other Loan Documents;  and any
action,  consent or waiver  (other than a compromise  of principal and interest)
when  given or taken by  Lender's  agent for  notice,  shall be deemed to be the
action of the  holders of a majority  in amount of the  Principal  Amount of the
Debenture,  as such holders are recorded on the books of the Borrower, and (iii)
in compliance with the legend to read as follows:

     "This Debenture has not been  registered  under the Securities Act of 1933,
     as amended ("Act"), or applicable state securities laws ("State Acts"), and
     shall not be sold,  hypothecated,  or  otherwise  transferred,  unless such
     transfer is made in compliance with the Act and the State Acts."

     The  Company  shall be  entitled  to treat  any  holder  of  record  of the
Debenture  as the Holder in fact thereof and of the  Debenture  and shall not be
bound to recognize any equitable or other claim to or interest in this Debenture
in the name of any other  person,  whether or not it shall have express or other
notice thereof, except as otherwise provided by applicable law.

     14. NOTICES.  All notices and communications  under this Debenture shall be
in writing and shall be either delivered in person or by overnight service, such
as FedEx, and accompanied by a signed receipt  therefor;  or mailed  first-class
United States certified mail,  return receipt  requested,  postage prepaid,  and
addressed as follows: (i) if to the Borrower at its address for notice as stated
in the Convertible Loan Agreement;  and (ii) if to the Holder of this Debenture,
to the address (a) of such Holder as it appears on the books of the  Borrower or
(b) in the case of a partial assignment to one or more Holders,  to the Lender's
agent for  notice,  as the case may be.  Any  notice of  communication  shall be
deemed given and received as of the date of such  delivery if  delivered;  or if
mailed, then three days after the date of mailing.

     15. MAXIMUM INTEREST RATE.

         (a)  Regardless of any provision  contained in this  Debenture,  Lender
shall  never be  entitled  to  receive,  collect  or apply  as  interest  on the
Debenture any amount in excess of interest  calculated at the Maximum Rate, and,
in the event that Lender ever receives, collects or applies as interest any such
excess,  the amount  which would be excessive  interest  shall be deemed to be a
partial  prepayment  of principal  and treated  hereunder  as such;  and, if the
principal  amount of the Debenture is paid in full,  any remaining  excess shall
forthwith be paid to Borrower.  In determining  whether or not the interest paid
or payable under any specific  contingency  exceeds  interest  calculated at the
Maximum Rate,  Borrower and Lender shall, to the maximum extent  permitted under
applicable law, (i) characterize any non principal payment as an expense, fee or
premium  rather than as interest,  (ii) exclude  voluntary  prepayments  and the
effects thereof,  and (iii) amortize,  pro rate,  allocate and spread,  in equal
parts, the total amount of interest  throughout the entire  contemplated term of
the  Debenture;  provided  that,  if the Debenture is paid and performed in full
prior to the end of the full  contemplated  term  thereof,  and if the  interest
received for the actual period of existence thereof exceeds interest  calculated


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<PAGE>


at the Maximum  Rate,  Lender shall refund to Borrower the amount of such excess
or  credit  the  amount  of such  excess  against  the  principal  amount of the
Debenture  and,  in such  event,  Lender  shall not be subject to any  penalties
provided  by any  laws for  contracting  for,  charging,  taking,  reserving  or
receiving interest in excess of interest calculated at the Maximum Rate.

         (b) "Maximum Rate" shall mean, on any day, the highest nonusurious rate
of interest (if any)  permitted by applicable  law on such day that, at any time
or from  time to time,  may be  contracted  for,  taken,  reserved,  charged  or
received on the Indebtedness evidenced by the Debenture under the laws which are
presently in effect of the United  States of America or by the laws of any other
jurisdiction  which are or may be applicable to the Holders of the Debenture and
such Indebtedness or, to the extent permitted by law, under such applicable laws
of the United States of America or by the laws of any other  jurisdiction  which
are or may be  applicable to the Holder of the Debenture and which may hereafter
be in effect and which allow a higher  maximum  nonusurious  interest  rate than
applicable laws now allow.

     16.   CONVERTIBLE   LOAN  AGREEMENT,   GUARANTY  AND  SECURITY  AND  PLEDGE
AGREEMENTS. This Debenture is issued pursuant to the Convertible Loan Agreement,
and the  Holder is  entitled  to all the rights and  benefits  thereunder.  Both
Borrower and the Holder have  participated in the negotiation and preparation of
the  Convertible  Loan Agreement and of this  Debenture.  Borrower agrees that a
copy of the  Convertible  Loan  Agreement  with all  amendments,  additions  and
substitutions  therefor  shall be  available  to the  Holder at the  offices  of
Borrower.  The  indebtedness  evidenced by this Debenture is secured pursuant to
the  Security  and  Pledge  Agreements  dated of even  date  herewith  among the
Company,  its  subsidiaries  and the  Holder,  and the Holder is entitled to all
rights and benefits of a secured party  thereunder.  The payment and performance
of this Debenture is guaranteed by the Company's  subsidiaries pursuant to their
Guaranty dated of even date herewith.

     17. DEFINED TERMS. Capitalized terms used but not defined herein shall have
the meaning given them in the Convertible Loan Agreement.

     18.  GOVERNING LAW. This  Debenture  shall be governed by and construed and
enforced in accordance with the substantive laws of the State of Texas,  without
regard to the conflicts of laws provisions  thereof,  and the applicable laws of
the United States.

     IN WITNESS  WHEREOF,  the  Company  has caused  this  Debenture  to be duly
issued, executed and delivered on the date and year above stated.



                               SIMTEK CORPORATION



                               By: /s/Douglas Mitchell
                                   -------------------------
                                   Name: Douglas Mitchell
                                         --------------------------------------
                                   Title: Chief Executive Officer and President
                                         --------------------------------------




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