Proposed is a novel chemical-sensitization resist composition capable of giving a positively or negatively patterned resist layer of excellent pattern resolution and cross sectional profile of the patterned resist layer with high sensitivity. Characteristically, the resist composition is formulated, as combined with a resinous ingredient which is subject to changes in the solubility behavior in an alkaline developer solution by interaction with an acid, with a specific oximesulfonate compound as the radiation-sensitive acid-generating agent represented by the general formula R1—C(CN)═N—O—SO2—R2, in which R1 is an inert organic group and R2 is an unsubstituted or substituted polycyclic monovalent hydrocarbon group selected from the group consisting of polycyclic aromatic hydrocarbon groups such as naphthyl and polycyclic non-aromatic hydrocarbon groups such as a terpene or camphor residue.