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The polymer comprising recurring units having formula 65 (2) functions such that it may be decomposed to generate carboxylic acid under the action of an acid and turn alkali 

soluble. The acid labile group represented by XA may be selected from a variety of such groups. Examples of the acid labile group include groups of the following general formu› lae (Ll) to (L4), tertiary alkyl groups of 4 to 20 carbon atoms, preferably 4 to 15 carbon atoms, trialkylsilyl groups in which each alkyl moiety has 1 to 6 carbon atoms, and oxoalkyl groups of 4 to 20 carbon atoms. 

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In formula (Ll), RLoi and RL $^{02 }$are hydrogen or straight, branched or cyclic alkyl groups of 1 to 18 carbon atoms, preferably 1 to 10 carbon atoms. Exemplary alkyl groups include methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, cyclopentyl, cyolohexyl, 2-ethylhexyl, n-octyl, norbornyl, tricyclodecanyl, tetracyclododecanyl, and ada› mantyl. RL $^{03 }$is a monovalent hydrocarbon group of 1 to 18 carbon atoms, preferably 1 to 10 carbon atoms, which may contain a heteroatom such as oxygen, examples of which include unsubstituted straight, branched or cyclic alkyl groups and straight, branched or cyclic alkyl groups in which some hydrogen atoms are replaced by hydroxyl, alkoxy, oxo, amino, alkylamino or the like, or in which an oxygen atom intervenes between carbon atoms. Exemplary straight, branched or cyclic alkyl groups include methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, cyclo› pentyl, cyclohexyl, 2-ethylhexyl, n-octyl, norbornyl, tricy› clodecanyl, tetracyclododecanyl, and adamantyl. Illustrative examples of the substituted alkyl groups are shown below. 

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A pair ofRLoi and RL 02 , RLoi and RL 03 , or RL $^{02 }$and RL 03 may bond together to form a ring with the carbon and oxygen atom to which they are attached. Each ofRL0 1 , RL 02 

