The chemically amplified negative resist, composed of polyvinylphenol derivative as a base resin, melamine derivative as a crosslinker and alkyl sulfonic acid derivative which has several number of carbon atoms (n equals 3, 4 and 8) as a photoacid generator PAG, has been investigated. The absorbance of this resist system remains constant even in the introduction of different alkyl sulfonic acid type PAG materials. The resolution, as well as the depth of focus, was not so different from each other within the carbon number from n equals 3 (n- and iso-propyl) to n equals 4 (n-butyl). In the case of n equals 8 (n-octyl), however, the resolution capability was degraded drastically and the depth of focus was also reduced. Furthermore, the carbon number of alkyl sulfonic acid affected the resist profile, that is, rounded profile (n equals 3) became rectangular (n equals 4) or overhang (n equals 8) profile. Especially, very heavy overhang profile was observed in the case of n equals 8, therefore, good resolution could not be achieved. And, the standing wave effect at the side wall increased with increasing carbon number. Relationship between lithographic performance and acid size was investigated by evaluating the dissolution rate characteristics. The fact that the dissolution kinetics were almost the same in the cases of n equals 3 and n equals 4 but degraded in the n equals 8, was consistent with lithographic performance as mentioned above. Based on these results, the most suitable acid size for this chemically amplified negative resist could be determined.