To provide a pattern formation method capable of forming a fine pattern with a short exposure wavelength light by using a composition comprising a specified poly(silsesquioxan), an acid generator, and an aliphatic cross- linking agent,

The resist pattern is formed by coating a substrate with a photosensitive composition comprising the 10-90 weight % poly(silsesquioxane) compound represented by the formula, a 0.01-20 weight % compound to be allowed to release a strong acid by irradiating with activated rays or radiation and a 5-60 weight % cross-linking agent. In the formula, each of R1 and R2 is, independently, an aliphatic or aromatic hydrocarbon group, preferably, having a hydroxy, carboxy, urthane, ureido, amido, or ester group, especially, the aliphatic hydrocarbon group having one of the above groups; and (n) is a polymerization degree.