The present invention provides a chemical amplification type positive resist composition comprising a nitrogen containing compound of the formula (VIa) or (VIb); ##STR00001## resin which contains a structural unit having an acid labile group and which itself is insoluble or poorly soluble in an alkali aqueous solution but becomes soluble in an alkali aqueous solution by the action of an acid; and an acid generator of the formula (I) ##STR00002##