A polymer is obtained from (meth)acrylate having a bridged ring lactone group, (meth)acrylate having an acid-labile leaving group, and (meth)acrylate having a hydroxynaphthyl pendant. A positive resist composition comprising the polymer as a base resin, when exposed to high-energy radiation and developed, exhibits a high sensitivity, a high resolution, and a minimal line edge roughness due to controlled swell during development, and leaves minimal residues following development.