PROBLEM TO BE SOLVED: To obtain a sulfonyl diazomethane compound suitable as a photo-acid generator for chemical amplification-type resist materials, or the like, for making integrated circuits sensitive to radiations including ultraviolet radiation, far-ultraviolet radiation, electron beams, X-rays, excimer laser, γ-rays and synchrotron radiation, to obtain such a photo-acid generator, to obtain such a resist material containing the sulfonyl diazomethane compound, and to provide a method for pattern formation using the resist material. SOLUTION: The sulfonyl diazomethane compound is represented by formula(1)( wherein, R is H or a 1-4C alkyl or alkoxy; G is SO 2 or CO; R 3 is a 1-10C alkyl or 6-14C aryl; (p) is 1 or 2, and (q) is 0 or 1, wherein p+q=2; (n) is 2 or 3; (n') is 0 or 1; (m) is an integer of 3-11; and (k) is an integer of 0-4 ). COPYRIGHT: (C)2004,JPO&NCIPI