Pattern forming method, semiconductor device manufacturing method and phase shift photomask having dummy gate patterns

Abstract

In a method for forming a plurality of gate patterns in parallel with each other on a photoresist layer within one circuit block, at least one dummy gate pattern is formed in parallel with the gate patterns when a pitch between said gate patterns is larger than a predetermined maximum pitch, so that pitches between the gate patterns including the dummy gate pattern are smaller than the predetermined maximum pitch. Then, a photolithography process is performed upon the photoresist layer by using a phase shift photomask having first and second openings whose difference in phase is π. The first and second openings alternate between the gate patterns including the dummy gate pattern to form phase edges therein.