Polymers, resist compositions and patterning process

A polymer comprising recurring units of the following general formulae (1a) and (1b) and having a weight average molecular weight of 1,000 to 500,000,

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• wherein R1 and R2 each are hydrogen, a fluorine atom or a straight, branched or cyclic alkyl or fluorinated alkyl group of 1 to 20 carbon atoms,
• R3 is a fluorine atom or a straight, branched or cyclic fluorinated alkyl group of 1 to 20 carbon atoms,
• R4 is an acid labile group, an adhesive group or a straight, branched or cyclic fluorinated alkyl group of 1 to 20 carbon atoms,
• R5 is an oxygen or sulfur atom,
• R6a, R6b, R6c and R6d are each independently hydrogen, a hydroxyl group, —(CH2)dC(R7)2(OR8), —(CH2)dCO2R8, or a straight, branched or cyclic alkyl or fluorinated alkyl group of 1 to 20 carbon atoms which may contain oxygen in the form of a hydroxyl group or ether bond in a substituent group,
• R7 is hydrogen, a fluorine atom or a straight, branched or cyclic fluorinated alkyl group of 1 to 20 carbon atoms,
• R8 is hydrogen, an acid labile group, an adhesive group, or a straight, branched or cyclic fluorinated alkyl group of 1 to 20 carbon atoms,
• letters a and b each are a number from more than 0 to less than 1, and 0<a+b≦1, c is 0 or 1, and d is a number of 0 to 6.