Negative resist composition and patterning process

A chemically amplified negative resist composition comprising a polymer as base resin, an acid generator and a crosslinker, said polymer comprising recurring units (a) and hydroxyl-containing recurring units (b), represented by the general formula (1):

• wherein R1 is a straight C1-C4 alkylene group, R2 is hydrogen, methyl or trifluoromethyl, R3 is hydrogen or methyl, Y1 is a single bond, —C(═O)—O— or —C(═O)—NH—, R4 is a single bond or a straight or branched C1-C6 alkylene group, R5 is hydrogen, fluorine, trifluoromethyl, cyano, or a straight, branched or cyclic C1-C6 alkyl, alkoxy, alkoxycarbonyl, acyl or acyloxy group, R6 is a single bond or a straight, branched or cyclic C1-C12 alkylene group, m is an integer of 0 to 4, n is 1 or 2, a and b are in the range:
• 0<a<1.0 and 0<b<1.0.