Polymers, resist compositions and patterning process

A polymer comprising recurring units of the following general formula (2a) to (2f) and recurring units of the following general (1c) or (1d) and having a weight average molecular weight of 1,000 to 500,000,

• wherein R2 is hydrogen, fluorine or a straight, branched or cyclic alkyl or fluorinated alkyl group of 1 to 20 carbon atoms, R3 and R4 each are a single bond or a straight, branched or cyclic alkylene or fluorinated alkylene group of 1 to 20 carbon atoms, R5 is hydrogen or an acid labile group, wherein R6, R7, R9, R10 and R17 each are a single bond or a straight, branched or cyclic alkylene or fluorinated alkylene group of 1 to 20 carbon atoms, R8, R11, R14 and R20 each are hydrogen or an acid labile group, R12, R13, R15, R16, R18 and R19 each are hydrogen, fluorine or a straight, branched or cyclic alkyl or fluorinated alkyl group of 1 to 20 carbon atoms, at least one of R18 and R19 contains at least one fluorine atom, R21 is a straight, branched or cyclic fluorinated alkyl group of 1 to 20 carbon atoms, “a” is 1 or 2, and each of b and c is 1 or 2, U11 and U12 are numbers satisfying 0<U11<1 and 0<U12<1.

A polymer comprising recurring units selected from the group consisting of the following general formulae and having a weight average molecular weight of 1,000 to 500,000,

• wherein R5 is hydrogen or an acid labile group, R8, R11 and R20 each are hydrogen or an acid labile group, U11 and U12 are numbers satisfying 0<U11<1 and 0<U12<1.