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[0122] It is noted that in the above formulae (L4-1) to (L4-4), (L4-3-l) and (L4-3-2), and (L4-4-1) to (L4-4-4), the bond direction is on the exo side relative to the bicyclo[2. 2.l]heptane ring, which ensures high reactivity for acid catalyzed elimination reaction (see JP-A 2000-336121). In preparing these monomers having a tertiary exo-alkyl group of bicyclo[2.2.l]heptane skeleton as a substituent group, there may be contained monomers substituted with an endo-alkyl group as represented by the following formulae (L4-1-endo) to (L4-4-endo ). For good reactivity, an exo proportion of at least 50 mo! % is preferred, with an exo proportion of at least 80 mo! % being more preferred. 

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Herein RL 41 is as defined above. 

[0123] Illustrative, non-limiting examples of the acid labile group of formula (L4) are given below. 

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[0124] Examples of the C$_{4}$ -C$_{20 }$ tertiary alkyl groups, tri› alkylsilyl groups in which each alkyl moiety has 1 to 6 carbon atoms, and C$_{4}$ -C$_{20 }$oxoalkyl groups, represented by XA, are as exemplified above for RL 04 . 

[0125] Illustrative examples of the recurring units of for› mula (a) are given below, but not limited thereto. Herein RA is as defined above. 

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