Fine pattern forming method

A fine pattern forming method, comprising the steps of:

• forming a high polymer organic film on a semiconductor substrate;
• forming a photosensitive layer on said high polymer organic film, said photosensitive layer comprising a ladder polysilicone resin insoluble in an alkaline solution and an acid generator which generates an acid when irradiated with an electron beam, said polysilicone resin including a Si--O bond in a principal chain and a group expressed as --OR in a side chain wherein R denotes a group which can be decomposed by an acid;
• forming a pattern with an electron beam on the photosensitive layer, thereby causing the generation of an acid by the acid generator, and baking the photosensitive layer to accelerate the decomposition reaction of the side chain by the generated acid to make the polysilicone resin in the pattern region soluble in an alkaline solution;
• developing the photosensitive layer with an alkaline aqueous solution to form a positive resist pattern;
• and
• etching the high polymer organic film by using the positive resist pattern as a mask.