A method and a resist composition. The resist composition includes a polymer having repeating units having a lactone moiety, a thermal base generator capable of generating a base and a photosensitive acid generator. The polymer has the properties of being substantially soluble in a first solvent and becoming substantially insoluble after heating the polymer. The method includes forming a film of a photoresist including a polymer, a thermal base generator capable of releasing a base, a photosensitive acid generator, and a solvent. The film is patternwise imaged. The imaging includes exposing the film to radiation, resulting in producing an acid catalyst. The film is developed in an aqueous base, resulting in removing base-soluble regions and forming a patterned layer. The patterned layer is baked above the temperature, resulting in the thermal base generator releasing a base within the patterned layer and the patterned layer becoming insoluble in the solvent.