EXHIBIT 5.1



                      [MORRISON & FOERSTER LLP LETTERHEAD]


                                October 22, 2002



Novellus Systems, Inc.
4000 North First Street
San Jose, CA 95134

Ladies and Gentlemen:


         At your request, we have examined the Registration Statement on Form
S-4, including the proxy statement-prospectus forming a part thereof, filed by
you with the Securities and Exchange Commission on August 29, 2002 and
subsequently amended (the "Registration Statement"), in connection with the
registration under the Securities Act of 1933, as amended, of 7,521,456 shares
of your common stock, no par value per share (the "Stock"). The Stock will be
issued to the former shareholders of SpeedFam-IPEC, Inc. ("SpeedFam"), an
Illinois corporation, pursuant to the terms of that certain Agreement and Plan
of Reorganization, dated as of August 11, 2002, by and among you, NHL
Acquisition-Sub, Inc., a Delaware corporation and your wholly-owned subsidiary,
and SpeedFam (the "Reorganization Agreement"). As counsel to the Company and in
connection with this opinion, we have examined all proceedings taken by you in
connection with the registration of the Stock.


         It is our opinion that the Stock, which is being issued by you in
exchange for the shares of common stock of SpeedFam pursuant to the
Reorganization Agreement, when issued in the manner described in the
Registration Statement, will be legally and validly issued, fully paid and
nonassessable.

         We consent to the use of this opinion as an exhibit to the Registration
Statement and further consent to all references to us in the Registration
Statement and any amendments thereto. In giving this consent, we do not thereby
admit that we are in the category of persons whose consent is required under
Section 7 of the Securities Act of 1933, as amended.

                               Very truly yours,

                               /s/ MORRISON & FOERSTER LLP