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                                                                    Exhibit 5.01

                  [Letterhead of Gibson, Dunn & Crutcher LLP]

                                 April 26, 2001

(212)351-4000                                                       C30814-00002

Fairchild Semiconductor Corporation
82 Running Hill Road
South Portland, Maine 04106

     Re:  Fairchild Semiconductor Corporation
          Registration Statement on Form S-4

Ladies and Gentlemen:

     We have acted as special counsel to Fairchild Semiconductor Corporation, a
Delaware corporation (the "Issuer"), Fairchild Semiconductor International,
Inc., the parent of the Issuer, and Fairchild Semiconductor Corporation of
California, a Delaware corporation, QT Optoelectronics, Inc., a Delaware
corporation, QT Optoelectronics, a California corporation, and KOTA
Microcircuits, Inc., a Colorado corporation (each a wholly-owned subsidiary of
the Issuer and collectively the "Guarantors"), in connection with the Issuer's
registration, on a Registration Statement on Form S-4 (the "Registration
Statement") under the Securities Act of 1933, as amended, of $350,000,000
aggregate principal amount of 10 1/2% Senior Subordinated Notes Due February 1,
2009 (the "New Notes"), which are to be guaranteed on a senior subordinated
basis pursuant to guarantees (the "Guarantees") by the Guarantors.

     The New Notes will be offered in exchange for like principal amounts of the
Issuer's outstanding 10 1/2% Senior Subordinated Notes Due February 1, 2009 (the
"Old Notes") pursuant to the Registration Rights Agreement, dated as of January
26, 2001 (the "Registration Rights Agreement"), among the Issuer, the
Guarantors, Credit Suisse First Boston Corporation, Lehman Brothers Inc.,
Deutsche Bank Alex. Brown Inc. and Fleet Securities Inc. The Registration Rights
Agreement was executed in connection with the private placement of the Old
Notes.

     The New Notes will be issued pursuant to the Indenture, dated as of January
31, 2001 (the "Indenture"), by and among the Issuer, the Guarantors and United
States Trust Company of New York, as Trustee.

     In rendering this opinion, we have made such inquiries and examined, among
other things, originals or copies, certified or otherwise identified to our
satisfaction, of such records, agreements, certificates, instruments and other
documents as we have considered necessary or appropriate for purposes of this
opinion. Further we have assumed that the signatures on all documents examined
by us are genuine, all individuals executing such documents had all requisite
legal capacity and competency and (except in the case of documents signed on
behalf of the Issuer and the Guarantors) were duly authorized, the documents
submitted to us as originals are authentic and the documents submitted to us as
certified or reproduction copies conform to the originals.

     Based on the foregoing and in reliance thereon, we are of the opinion that:

          (i) the New Notes have been duly authorized by the Issuer and, when
     issued in exchange for the Old Notes pursuant to the terms of the exchange
     offer described in the Registration Statement and the Indenture, will be
     validly issued and will constitute legal and binding obligations of the
     Issuer; and
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Fairchild Semiconductor Corporation
April 26, 2001
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          (ii) the Guarantees have been duly authorized by the Guarantors and
     will be validly issued and will constitute legal and binding obligations of
     the Guarantors.

     The foregoing opinions are subject to the following exceptions,
qualifications and limitations:

          A. Our opinions are subject to (i) the effect of any bankruptcy,
     insolvency, reorganization, moratorium, arrangement or similar laws
     affecting the rights and remedies of creditors' generally (including,
     without limitation, the effect of statutory or other laws regarding
     fraudulent transfers or preferential transfers) and (ii) general principles
     of equity, including without limitation concepts of materiality,
     reasonableness, good faith and fair dealing and the possible unavailability
     of specific performance, injunctive relief or other equitable remedies
     regardless of whether enforceability is considered in a proceeding in
     equity or at law.

          B. We express no opinion regarding the effectiveness of any waiver of
     stay, extension or usury laws or of unknown future rights.

          C. We render no opinion herein as to matters involving the laws of any
     jurisdiction other than the State of New York and the United States of
     America and, for purposes of paragraphs (i) and (ii) above, the General
     Corporation Law of the State of Delaware, and for purposes of paragraph
     (ii) above, the General Corporation Law of the State of California and the
     Business Corporation Act of the State of Colorado. We are not admitted to
     practice in the State of Delaware; however, we are generally familiar with
     the General Corporation Law of the State of Delaware as currently in effect
     and have made such inquiries as we consider necessary to render the
     opinions contained herein. This opinion is limited to the effect of the
     current state of the laws of the State of New York, the United States of
     America and, to the limited extent set forth above, the General Corporation
     Law of the State of Delaware, the General Corporation Law of the State of
     California and the Business Corporation Act of the State of Colorado and
     the facts as they presently exist. We assume no obligation to revise or
     supplement this opinion in the event of future changes in such laws or the
     interpretations thereof or such facts.

     We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement and to the reference to this firm under the heading
"Legal Matters" contained in the prospectus that forms a part of the
Registration Statement. In giving this consent, we do not admit that we are
within the category of persons whose consent is required under Section 7 of the
Securities Act of 1933, as amended, or the rules and regulations promulgated
thereunder.

                                          Very truly yours,

                                          /s/ GIBSON, DUNN & CRUTCHER LLP