The invention relates to a photomask for use in a thermal flow process in which: a photomask is prepared in which a plurality of exposure openings are formed; a resist is applied to the surface of a layer of a semiconductor integrated circuit that is to undergo processing; this resist is patterned by an exposure process through the photomask to form a plurality of openings in the resist that correspond to each of the exposure openings; and the patterned resist is then heated to cause each of the openings to shrink; wherein at least a portion of exposure openings among the plurality of exposure openings are formed in shapes that compensate for anisotropic deformation that occurs in the openings when the patterned resist is heated to cause each of the openings to shrink. Since the openings that are formed in the resist are provided in advance with shapes that compensate for the deformation that occurs when the openings shrink, these openings attain the proper shape after undergoing shrinking and deformation.