Patent ID: 7008736

Claim:
A semiconductor integrated circuit device fabrication method, comprising the steps of: disposing a semiconductor substrate having a photoresist film on a position in a projection exposure system; providing a mask comprising: (a) a phase shifting film covering region, over a flat major surface of a transparent mask substrate; (b) an opening region, in the phase shifting film covering region, there being no phase shifting film in the opening region; and (c) a shifter edge region of the phase shifting film covering region, which shifter edge region borders on and is adjacent to the opening region, the shifter edge region having a phase shifting film over the flat major surface of the transparent mask substrate; mounting the mask to the projection exposure system such that a front surface of the mask, with the phase shifting film formed thereon, faces down; and transferring the pattern formed on the mask onto the semiconductor substrate having the photoresist film with an exposure light flux, said exposure light flux being at least partially coherent in an ultraviolet domain and being transmitted through the mask from the back surface of the mask, without the phase shifting film, to the front surface of the mask, with the phase shifting film, wherein the exposure light flux is transmitted through the shifter edge region contacted with the border of the opening region and a phase of the transmitted exposure light flux transmitted through the shifter edge region is inverted with respect to that of the transmitted exposure light flux transmitted through the opening region, due to only said transmission through the phase shifting film, and whereby resolution is improved due to destructive interference between exposure light fluxes transmitted through the opening region and the shifter edge region.