PURPOSE: To superppose defocusing light on a proximate pattern and to increase a focus margin by exposing the surface of a substrate by using a mask varying in the phase of the light transmitted through the adjacent transmission patterns.

CONSTITUTION: The spacings between respective patterns are shortened as higher integration of devices progresses. Increase of resolving power and focus margin are requested in correspondence thereto. Exposure by a flex method is then executed by using the mask inverted in the phase of the transmitted light through halftone holes and dropout holes. The inversion of the phases is enabled simply by forming shifter patterns over the entire surface of transmission parts at the thickness having a phase difference of π from the transmission parts of the substrate in the same manner as for formation of ordinary phase shifters. The transmission film parts in the case of the phase shift reticule stressing the boundaries at the peripheral edges of the patterns are previously formed large and the phase shifters are formed in these parts and, therefore, the transmission film parts are large for the ordinary reticule and the parts of the light shielding films are small in the case of formation of the isolated patterns.