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). R1 is F or CF3, R2 and R3 are H or alkyl or form a ring, R4 is H or an acid labile group, R5 to R6 are H, F, or alkyl, or two of R5 to R8 may together form a ring, m=0 or 1, 0.2≦a≦0.8, and 0.1≦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.