
<PAGE>   1

                                                                     EXHIBIT 5.1

                                 June 20, 2001

Amkor Technology, Inc.
1345 Enterprise Drive
West Chester, PA 19380

        RE:     NEW 9.25% SENIOR NOTES DUE 2008 COVERED
                BY REGISTRATION STATEMENT ON FORM S-4

Ladies and Gentlemen:

         We have acted as corporate counsel to Amkor Technology, Inc., a
Delaware corporation (the "Company"), in connection with the filing by the
Company with the Securities and Exchange Commission (the "Commission") of a
registration statement on Form S-4 (the "Registration Statement") under the
Securities Act of 1933, as amended (the "Securities Act"). The Registration
Statement relates to the proposed issuance by the Company to exchange $1,000
principal amount of its 9.25 Senior Notes due 2008 (the "New Notes") for each
$1,000 principal amount of its outstanding 9.25% Senior Notes due 2008 (the "Old
Notes"), of which $500,000,000 aggregate principal amount is outstanding as of
the date hereof.

        The Old Notes are, and the New Notes will upon issuance be, covered by
that certain Indenture dated February 20, 2001 (the "Indenture") by and between
the Company and State Street Bank and Trust Company, as trustee (the "Trustee").
This opinion letter is delivered in accordance with the requirements of Item
601(b)(5) of Regulation S-K under the Securities Act.

         In connection with this opinion, we have examined originals or copies,
certified or otherwise identified to our satisfaction, of: (i) the Registration
Statement, in the form filed with the Commission; (ii) the Company's Certificate
of Incorporation and all amendments thereto, as currently in effect; (iii) the
Company's bylaws, as amended to date; (iv) the



<PAGE>   2

Amkor Technology, Inc.
June 20, 2001
Page 2


Indenture; (v) the form of the New Notes; and (vi) resolutions of the Board of
Directors of the Company relating to, among other things, the issuance and
exchange of the New Notes for the Old Notes and the filing of the Registration
Statement. We also have examined such other documents as we have deemed
necessary or appropriate as a basis for the opinions set forth below.

        In our examination, we have assumed the legal capacity of all natural
persons, the genuineness of all signatures, the authenticity of all documents
submitted to us as originals, the conformity to original documents of all
documents submitted to us as certified or photostatic copies, and the
authenticity of the originals of such latter documents. As to certain facts
material to this opinion, we have relied without independent verification upon
oral or written statements and representations of officers and other
representatives of the Company and others.

        Based upon the foregoing, and subject to the assumptions and limitations
set forth herein, we are of the opinion that, when (i) the Registration
Statement, as finally amended (including all necessary post-effective
amendments, if any), shall have become effective under the Securities Act and
(ii) when the New Notes are duly executed, attested, issued and delivered by
duly authorized officers of the Company, and authenticated by the Trustee, all
in accordance with the terms of the Indenture and the prospectus contained in
the Registration Statement, against surrender and cancellation of a like
principal amount of Old Notes, the New Notes issued by the Company will be
legally issued, and the New Notes will constitute valid and binding obligations
of the Company, enforceable against the Company in accordance with their terms,
except to the extent that enforcement thereof may be limited by (i) bankruptcy,
insolvency, reorganization, arrangement, moratorium, fraudulent conveyance and
other laws relating to or affecting creditors' rights generally, and (ii)
general principles of equity, whether such enforcement is considered in a
proceeding in equity or at law.

        To the extent relevant to the opinions set forth above, we have assumed
that the Trustee is duly organized, validly existing and in good standing under
the laws of its jurisdiction of organization; that the Trustee is duly qualified
to engage in the activities contemplated by the Indenture and is duly qualified
and eligible under the terms of the Indenture to act as trustee thereunder; that
the Indenture was duly authorized, executed and delivered by the Trustee; that
the Indenture is a valid and binding obligation of the Trustee; that the Trustee
is in compliance, generally with respect to acting as a trustee under the
Indenture, with all applicable laws and regulations; and that the Trustee has
the requisite organizational and legal power and authority to perform its
obligations under the Indenture.

        This opinion is given in respect of the Indenture and the New Notes
only, and we express no opinion as to the legality, validity or binding effect
of any collateral agreement or other document or any other matter beyond the
matters expressly set forth herein.

        We express no opinion as to the enforceability of provisions of the
Indenture or the New Notes that provide that the assertion or employment of any
right or remedy shall not prevent the concurrent assertion or employment of any
other right or remedy, or that every right and remedy shall be cumulative and in
addition to every other right and remedy, or that any delay or


<PAGE>   3

Amkor Technology, Inc.
June 20, 2001
Page 3


omission to exercise any right or remedy shall not impair any other right or
remedy or constitute a waiver thereof.

         Members of our firm are admitted to the bars of the State of California
and the State of New York, and we do not express any opinion as to the laws of
any jurisdiction other than the laws of the State of California and the State of
New York, the General Corporation Law of the State of Delaware and the federal
laws of the United States, and we express no opinion with respect to the
applicability thereto, or the effect thereon, of the laws of any other
jurisdiction. Moreover, we express no opinion with respect to compliance with
state securities laws or as to the applicability to the obligations of the
Company under the Indentures or the New Notes of Sections 547 and 548 of Title
11 of the United States Code or applicable state law (including, without
limitation, Article 10 of the New York Debtor & Creditor Law and Sections 3439
et seq. of the California Civil Code) relating to fraudulent transfers.

        This opinion is rendered solely for your benefit in connection with the
transactions described above. This opinion may not be used or relied upon by any
other person and may not be disclosed, quoted, filed with a governmental agency
or otherwise referred to without our prior written consent. However, we consent
to the filing of this opinion as an exhibit to the Registration Statement and
prospectus and to the use of our name under the caption "Legal Matters" in the
Registration Statement and any amendments thereto. In giving such consent, we do
not concede that we are experts within the meaning of the Securities Act or the
rules and regulations thereunder or that this consent is required by Section 7
of the Securities Act.

                                        Very truly yours,

                                        WILSON SONSINI GOODRICH & ROSATI
                                        Professional Corporation

                                        /s/ Wilson Sonsini Goodrich
                                            & Rosati, P.C.


