PURPOSE: To form a pattern high in resolution with high sensitivity by forming on a substrate a thin film a polymer having in the molecule, chalkone groups each substd. by an electron donor group as a photosensitive group, selectively irradiating UV rays, and then, eluting the unexposed parts with a developing soln. to develop it.

CONSTITUTION: A methyl or methoxy group is introduced into each chalkone group of a chalkone type polymer, embodied by a copolymer of 4'-methacryloylchalkone or 4-methacryloylchalkone, and methacrylate, such as methyl methacrylate, butyl methacrylate, or glycidyl methacrylate, and such introduction can shift its photosensitivity to a long wavelength side. For example, a substrate is coated with a resist of a copolymer of glycidyl methacrylate, and prebaked in the air, the desired parts of the resist film are irradiated with 365nm UV ray, and then developed. A necessary 365nm ray irradiation time is shortened to 1/3W 1/6 as short as that of the conventional chalkone type resists and a pattern high in resolution can be obtained.