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diethylpropyl, 2-cyclopentylpropan-2-yl, 2-cyclohexylpro› pan-2-yl, 2-(bicyclo[2.2.l]heptan-2-yl)propan-2-yl, 2-(ada› mantan-1-yl)propan-2-yl, 1-ethylcyclopentyl, 1-butylcyclopentyl, 1-ethylcyclohexyl, 1-butylcyclohexyl, l-ethyl-2-cyclopentenyl, l-ethyl-2-cyclohexenyl, 2-methyl- 2-adamantyl, and 2-ethyl-2-adamantyl. Exemplary trialkyl› silyl groups include trimethylsilyl, triethylsilyl, and dim› ethyl-tert-butylsilyl. Exemplary oxoalkyl groups include 3-oxocyclohexyl, 4-methyl-2-oxooxan-4-yl, and 5-methyl- 2-oxooxolan-5-yl. Letter x is an integer of O to 6. 

[0109] In formula (L3), RLos is an optionally substituted C 1 -Cg alkyl group or an optionally substituted CcC$_{20 }$ aryl group. The optionally substituted alkyl group may be straight, branched or cyclic and examples thereof include methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert› butyl, tert-pentyl, n-pentyl, n-hexyl, cyclopentyl and cyclo› hexyl, and substituted forms of the foregoing in which some hydrogen is substituted by hydroxyl, alkoxy, carboxyl, alkoxycarbonyl, oxo, amino, alkylamino, cyano, mercapto, alkylthio, sulfa or the like. Examples of the optionally substituted aryl groups include phenyl, methylphenyl, naph› thyl, anthryl, phenanthryl, and pyrenyl, and substituted forms of the foregoing in which some hydrogen is substi› tuted by hydroxyl, alkoxy, carboxyl, alkoxycarbonyl, oxo, amino, alkylamino, cyano, mercapto, alkylthio, sulfa or the like. Letter y is equal to O or 1, z is an integer ofO to 3, and 2y+z is equal to 2 or 3. 

[0110] In formula (L4), RL $^{06 }$is an optionally substituted C 1 -Cg alkyl group or an optionally substituted C 6 -C 20 aryl group. Examples of the alkyl and aryl groups are the same as exemplified for RL0 5 • 07 16 

[0111] RL to RL are each independently hydrogen or an optionally substituted C 1 -C 15 monovalent hydrocarbon group. Suitable hydrocarbon groups include straight, branched or cyclic alkyl groups such as methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, tert-pentyl, n-pentyl, n-hexyl, n-octyl, n-nonyl, n-decyl, cyclopentyl, cyclohexy I, cyclopenty lmethy I, cyclopenty lethy I, cyclopen› ty lbuty l, cyclohexylmethyl, cyclohexylethyl and cyclohex› ylbutyl, and substituted forms of the foregoing in which some hydrogen is substituted by hydroxyl, alkoxy, carboxyl, alkoxycarbonyl, oxo, amino, alkylamino, cyano, mercapto, alkylthio, sulfa or the like.Alternatively, two ofRL 07 to RL 16 may bond together to form a ring with the carbon atom to which they are attached (for example, a pair of RL 07 and RLOg’ RLo7 and RLo9, RLo7 and RLio, RLog and RLio, RLo9 and RLI 0 , RL 11 and RL 12 , RL 13 and RL 14 , or a similar pair form a ring). Each of RL 07 to RL 16 represents a divalent C 1 -C 15 hydrocarbon group when they form a ring, examples of which are the ones exemplified above for the monovalent hydrocarbon groups, with one hydrogen atom being elimi› nated. Two of RL 07 to RL 16 which are attached to vicinal carbon atoms may bond together directly to form a double bond (for example, a pair ofRL 07 and RL 09 , RL $^{09 }$and RLI 5 , RL 13 and RLI 5 , RL 14 and RL 15 , or a similar pair). 

[0112] Of the acid labile groups having formula (Ll), the straight and branched ones are exemplified by the following groups, but not limited thereto. 

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[0113] Of the acid labile groups having formula (Ll ), the cyclic ones are, for example, tetrahydrofuran-2-yl, 2-meth› yltetrahydrofuran-2-yl, tetrahydropyran-2-yl, and 2-methyl› tetrahydropyran-2-yl. 

[0114] Examples of the acid labile group having formula (L2) include tert-butoxycarbonyl, tert-butoxycarbonylm› ethyl, tert-pentyloxycarbonyl, tert-pentyloxycarbonylm› ethyl, 1, 1-diethylpropyloxycarbonyl, 1, 1-diethylpropyloxy› carbonylmethyl, 1-ethylcyclopentyloxycarbonyl, 1-ethy lcyclopenty loxycarbony lmethy I, 1-ethy 1-2-cyclopen› tenyloxycarbonyl, 1-ethy 1-2-cyclopenteny loxycarbony !m› ethyl, 1-ethoxyethoxycarbonylmethyl, 2-tetrahydropyrany› loxycarbonylmethyl, and 2-tetrahydrofuranyloxycarbonylmethyl groups. 

[0115] Examples of the acid labile group having formula (L3) include 1-methylcyclopentyl, 1-ethylcyclopentyl, 1-n› propylcyclopentyl, 1-isopropylcyclopentyl, 1-n-butylcyclo› pentyl, 1-sec-butylcyclopentyl, 1-cyclohexylcyclopentyl, 1-( 4-methoxy-n-butyl)cyclopentyl, 1-methylcyclohexyl, 1-ethy lcyclohexy I, 3-methy 1-1-cyclopenten-3-y I, 3-ethy 1-1- cyclopenten-3-y l, 3-methyl-1-cyclohexen-3-yl, and 3-ethyl› l-cyclohexen-3-yl groups. 

[0116] Of the acid labile groups having formula (L4), groups having the following formulas (L4-1) to (L4-4) are preferred. 

