To ensure high sensitivity to active radiation such as far UV and high resolution, to form a resist pattern excellent in dimensional precision and to enable development with an aq. alkali soln. by incorporating a specified medium reactive with acid as catalyst, a compd. generating an acid when irradiated and a basic compd. forming an acidic intermediate by exposure.

This radiation sensitive compsn. contains a medium having such reactivity as to vary solubility to an aq. alkali soln. by reaction with an acid as a catalyst, a compd. generating an acid when irradiated and a basic compd. forming an acidic intermediate by exposure. The acidic intermediate reacts effectively on the medium as well as on the acid catalyst generated by irradiation and can further considerably vary the solubility of the exposed part. The basic compd. existing in the unexposed part can inhibit or prevent catalytic reaction by the acid diffused from the exposed part and can improve pattern shape, etc.