To provide a positive type chemically amplified photosensitive resin composition having high sensitivity, high resolution and a good pattern shape as a positive type chemically amplified photosensitive resin composition in which a pattern is allowed to appear by patternwise irradiating the composition with radiation such as UV, far UV, X-rays or electron beams, generating an acid in the patterned latent image forming part and making the solubility of the irradiated part to an alkali developing solution different from that of the unirradiated part by a reaction catalyzed by the acid and a method for producing a resist image using the composition.

In the photosensitive resin composition containing (a) a resin soluble in an aqueous alkali solution, (b) a compound which generates an acid when irradiated with active actinic radiation and (c) a compound having solubility to the aqueous alkali solution increased by an acid catalyzed reaction and having an acid decomposable group in a side chain, the molecular weight of the compound (c) is 1,000-10,000. A coating of the photosensitive resin composition is irradiated with active actinic radiation and developed to produce the objective resist image.