Abstract: A copolymer of sulfur dioxide and polyalkylpolysilylstyrene composed of repeating units of formula I: ##STR1## where R is a lower alkyl group, p is an integer between 2 and 5, q in an integer between 1 and 10 representing the sequence length of polyalkylpolysilylstyrene, and n is a number between 5 and 10,000, and having a number-average molecular weight of 2,000 to 2,000,000. This copolymer is a novel and useful positive resist material which is highly sensitive to light, or electron-beam or X-ray radiation and is of high dry etching resistance.