EXHIBIT 5.1


December 9, 2002

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


Ladies and Gentlemen:

               We have examined the Registration Statement on Form S-8 to be
filed by Novellus Systems, Inc., a California corporation (the "Company"), with
the Securities and Exchange Commission on December 9, 2002 (the "Registration
Statement"), relating to the registration under the Securities Act of 1933, as
amended, of 1,674,728 shares of Common Stock, no par value, of the Company (the
"Stock") for issuance pursuant to options granted or to be granted under the
SpeedFam, Inc. 1991 Employee Incentive Stock Option Plan, as amended, the
SpeedFam-IPEC, Inc. 1992 Stock Option Plan, as amended, the 1995 Stock Plan for
Employees and Directors of SpeedFam-IPEC International, Inc., as amended, the
2001 Nonstatutory Stock Option Plan of SpeedFam-IPEC, Inc., and the Stand-Alone
Nonstatutory Stock Option Agreement of SpeedFam-IPEC, Inc., dated June 14, 2001
assumed by the Company. As counsel to the Company, we have examined the
proceedings taken by the Company in connection with the registration of the
Stock.

               It is our opinion that the Stock, when issued and sold in the
manner described in the Registration Statement and the related Prospectus, 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.

                                        Very truly yours,

                                        /s/ Morrison & Foerster, LLP