A resist composition contains a base resin, a photoacid generator, and a solvent. The photoacid generator is a sulfonium salt of formula (1). R1 is hydroxyl, nitro, or straight, branched or cyclic monovalent C1-15 hydrocarbon group which may contain O, N or S, and two R1 groups may form a ring together wherein the R1 groups are straight, branched or cyclic divalent C1-15 hydrocarbon groups which may contain O, N or S, K− is a non-nucleophilic counter ion, x is 1 or 2, and y is 0, 1, 2 or 3. The resist composition is sensitive to ArF excimer laser light, has good sensitivity and resolution, and forms a thick film which is advantageous in etching.