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In the case of a monomer having a hydroxyl group, the hydroxyl group may be replaced by an acetyl, acetal or simi- lar group at the monomer stage, and the polymerization be followed by deprotection reaction to restore the hydroxyl 

group. Where the hydroxyl group is replaced by an acetyl group, the polymerization may be followed by alkaline hydrolysis to deprotect the acetyl group into a hydroxyl group. Where the hydroxyl group is replaced by an acid labile group such as acetal, deprotection via hydrolysis with an acid catalyst may be carried out to restore a hydroxyl group. 

In addition to the recurring units (p ), ( q 1) and ( q2) in formula (2), the polymer to be added to the resist composition may have further copolymerized therein recurring units (r) having a carboxyl group for the purposes of improving alkali solubility and rendering the resist film after development more hydrophilic. 

Examples of the recurring units (r) having a carboxyl group are given below. 

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