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[0086] The attachment of an acid generator to the polymer main chain is effective in restraining acid diffusion, thereby preventing a reduction of resolution due to blur by acid diffusion. Also edge roughness is improved since the acid generator is uniformly distributed. Where a base polymer containing recurring units (f) is used, the addition of a separate PAG (to be described later) may be omitted. 

[0087] The base polymer for formulating the positive resist composition comprises recurring units (al) or (a2) having an acid labile group as essential component and additional recurring units (b ), ( c ), ( d), ( e ), and (f) as optional components. A fraction of units (al), (a2), (b), (c), (d), (e), and (f) is: preferably 0sal <1.0, 0sa2<1.0, 0<al +a2<1.0, 0sbs0.9, 0scs0.9, 0sds0.8, 0ses0.8, and 0sfs0.5; more preferably 0sals0.9, 0sa2s0.9, 0.lsal+a2s0.9, 0sbs0.8, 0scs0.8, 0sds0.7, 0ses0.7, and 0sfs0.4; and even more preferably 0sals0.8, 0sa2s0.8, 0.lsal+a2s0.8, 0sbs0.75, 0scs0.75, 0sds0.6, 0ses0.6, and 0sfs0.3. Notably, f=fl+ f2+f3, meaning that unit (f) is at least one of units (fl) to (f3), and al+a2+b+c+d+e+f=l.0. 

[0088] For the base polymer for formulating the negative resist composition, an acid labile group is not necessarily essential. The base polymer comprises recurring units (b ), and optionally recurring units (c), (d), (e), and/or (f). A fraction of these units is: preferably 0<bsl.0, 0scs0.9, 0sds0.8, 0ses0.8, and 0sfs0.5; more preferably 0.2sbsl .0, 0scs0.8, 0sds0.7, 0ses0.7, and 0sfs0.4; and even more preferably 0.3sbsl.0, 0scs0.75, 0sds0.6, 0ses0.6, and 

