A copolymer of t-butyl-3 alpha-(5-norbomene-2-carbonyloxy)-7 alpha,12 alpha-dihydroxy-5 beta-cholan-24-oate and maleic anhydride was synthesized as a matrix polymer for ArF excimer laser lithography. The polymer has an excellent transmittance at 193 nm and possesses good thermal stability up to 255 degrees C, The resist formulated with the polymer showed better dry-etching resistance than the conventional KrF excimer laser resist for chlorine and oxygen mixed gas. A 0.15 mu m line and space patterns were obtained at a dose of 18 mJ cm(-2) using an ArF excimer laser stepper.