Patent ID: 7144674

Claim:
A positive resist composition comprising (A) resin which is itself insoluble or poorly soluble in an alkali aqueous solution but due to a chemical change by the action of an acid becomes soluble in an alkali aqueous solution with a proviso that the resin is not novolak resin and has a structural unit of the following formula (I): wherein R 1 represents alkyl having 1 to 4 carbon atoms, and R 2 represents alkyl having 1 to 6 carbon atoms or cycloalkyl having 5 to 7 carbon atoms, or R 1 and R 2 bond to form trimethylene chain or tetramethylene chain, (B) novolak resin containing a structural unit having a phenolic hydroxyl group partially protected with an acetal group which can be dissociated by the action of an acid and (C) an acid generator.