To attain the compatibility of the improvement in the resolution characteristic in the far UV region of a halftone phase shift mask with the improvement in the characteristic to be inspected or handling quality in a visible light region.

A halftone phase shifter 2a consisting of an MoSix film is formed on a glass substrate 1 and the surface layer part of the glass substrate 1 exposed within its openings 5 is subjected to ion implantation of Ga+, by which low-transmittance regions 6 are formed. Even if the absolute light transmittance of the halftone phase shifter 2a at a KrF excimer laser wavelength (248nm) is set at 6% like heretofore, the relative light trarismittance of a half tone part to the light transmitted through the substrate is increased to (6/75)×100=8% by setting the absolute light transmittance of the low- transmittance regions 6 to 75%, thereby attenuating the light transmitted through the substrate. The defect inspection in the visible light region is thereby executed as easily as heretofore and the good resolution is obtd. by suppressing the secondary peak in the actual exposure wavelength region.