b1 80 20 mol after polymerization the reaction mixture was added dropwise to 500 ml of n hexane to thereby solidify and purify the resulting resin and the generated white powder was filtered on a membrane filter and washed with n hexane 1000 ml the white powder was collected and dried overnight under reduced pressure at 40 u00b0 c to obtain methacrylic copolymer p6 6 42 g the methacrylic copolymers p1 to p6 each in an amount of 100 parts by weight and 10 parts by weight of triphenylsulfonium nonafluorobutanesulfonate tps 109 midori kagaku co ltd japan were dissolved in an ethyl lactate solvent to give a copolymer concentration of 6 3 by weight thereby preparing photosensitive resin compositions r 1 to r 6 after an antireflection coating arc 29 nissan chemical industries ltd japan was applied onto a silicon wafer each photoresist resin composition was applied onto the antireflection coating by spin coating to thereby form a photosensitive layer of 100 nm thickness after pre exposure bake on a hot plate at a temperature of 90 u00b0 c for 60 seconds each photosensitive layer was irradiated in a 75 nm half pitch line and space pattern 10 lines using an electron beam lithography system els 7700 elionix inc japan followed by post exposure bake peb at a given temperature for 90 seconds then each photosensitive layer was developed for 60 seconds with 0 3 m aqueous tetramethylammonium hydroxide and rinsed with pure water to obtain a line and space pattern the same procedure as shown in example 5 was repeated to obtain methacrylic copolymer p7 14 1 g except that monomer l1 was replaced with u03b1 methacryloyloxy u03b3 butyrolactone hereinafter.