To form a high definition pattern by incorporating an alkali-soluble resin, a compound whose solubility in an aqueous alkali solution is increased by the action of radiation and a compound which forms an alkali-soluble group under a base.

The positive type radiation sensitive resist composition contains an alkali-soluble resin, a compound whose solubility in an aqueous alkali solution is increased by the action of radiation and one or more compounds which are decomposed by the action of a base and form an alkali-soluble group as principal components. The alkali-soluble group is not limited if it increases solubility in the aqueous alkali solution as a developing solution and the group is preferably a carboxyl group or a phenolic hydroxyl group. In the exposed part into which the aqueous alkali solution penetrates rapidly, the decomposition of the compounds and solubilization proceed rapidly and the velocity of dissolution increases.