A resist composition comprises a base polymer which changes its alkali solubility under the action of an acid, and an additive copolymer comprising recurring units (a) and (b). R.sup.1 is F or CF.sub.3, R.sup.2 and R.sup.3 are H or alkyl or form a ring, R.sup.4 is H or an acid labile group, R.sup.5 to R.sup.6 are H, F, or alkyl, or two of R.sup.5 to R.sup.8 may together form a ring, m=0 or 1, 0.2.ltoreq.a.ltoreq.0.8, and 0.1.ltoreq.b 0.6. A resist film of the composition has good barrier property against water so that leaching of the resist film with water is controlled, minimizing a change of pattern profile due to leach-out. ##STR00001##