PURPOSE: To provide a halftone system phase shift mask having a phase shift layer of a uniform film thickness and a process for producing this mask.

CONSTITUTION: This halftone system phase shift mask is a phase shift mask which has light transmissive regions 40 and half light shielding regions 42 and varies in the phases of the light transmitting through the half light shielding regions and the light transmitting through the light transmissive regions. The phase shift mask has a substrate 32 consisting of quartz, an etching stopper layer 34 formed on the substrate, the half light shielding regions consisting of the phase shift layer 36 and metallic thin film 38 successively laminated on this etching stopper layer and the light transmissive regions exposed with the etching stopper layer 34 by opening into the half light shielding regions. The end of the etching is regulated by the etching stopper layer 34, by which the film thickness of the phase shift layer 36 is exactly controlled.