A method for forming a fine pattern in a semiconductor substrate, by coating a target layer to be etched on a semiconductor substrate with a resist composition including at least one compound capable of forming a photoresist pattern by a photolithography process, and a free radical initiator. The free radical initiator is capable of being decomposed by a thermal process at a temperature equal to or higher than the glass transition temperature of the at least one compound. A lithography process is performed on the resist compound layer to form a photoresist pattern. The resist compound layer having the photoresist pattern formed therein is heated to a temperature equal to or higher than the glass transition temperature of the at least one compound, and wherein a partial cross-linking reaction in the resist composition occurs.