The invention provides a halftone phase shift photomask that is of much more simplified structure and so can be fabricated much more easily, which comprises a transparent substrate 10 and a single halftone light-blocking and phase shift layer 11 that is formed on the surface thereof according to a predetermined pattern and is made up of a material of homogeneous composition, characterized in that:said single halftone light-blocking and phase shift layer has a film thickness d that is virtually equal to a value defined byd=.lambda./{2(n-1)}where .lambda. is the wavelength at which the photomask is used, and n is the index of refraction of the single layer, or that is an odd-numbered multiple of said value, and has a transmittance lying substantially in the range of 5 to 30%. The layer 11 may be made up of any of CrO.sub.x, CrN.sub.x, CrO.sub.x N.sub.y and CrO.sub.x N.sub.y C.sub.z.