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fluorinated alkyl group of 1 to 5 carbon atoms, and is most preferably a hydrogen atom or a methyl group. 1 

There are no particular limitations on X as long as it is an acid-dissociable group. Examples include the aforemen› tioned tertiary alkyl ester-type acid-dissociable groups and acetal-type acid-dissociable groups, and of these, a tertiary alkyl ester-type acid-dissociable group is preferable. 

In the general formula (al-0-2), R is the same as defined above. 2 1 

X is the same as defined for X in formula (al-0-1). 

Although there are no particular limitations on the divalent linking group for Y 2 , preferred examples include divalent hydrocarbon groups which may have a substituent, and diva› lent linking groups containing a hetero atom. Specific examples of these divalent hydrocarbon groups which may have a substituent, and divalent linking groups containing a hetero atom include the same divalent linking groups as those described above for R 0 $_{-}$1 in the general formula (a0-0-1) within the description relating to the structural unit (a0). 2 

Y is preferably a linear or branched alkylene group, a divalent alicyclic hydrocarbon group, or a divalent linking group containing a hetero atom. 2 

When Y is a linear or branched alkylene group, the alky› lene group preferably contains 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms, still more preferably 1 to 4 carbon atoms, and most preferably 1 to 3 carbon atoms. Specific examples include the same linear alkylene groups and branched alkylene groups as those mentioned above for the linear or branched aliphatic hydrocarbon group within the description of the divalent linking group for R 0 $_{-}$1 . When Y 2 is a divalent alicyclic hydrocarbon group, examples of the ali- cyclic hydrocarbon group include the same alicyclic hydro› carbon groups as those mentioned above as the "aliphatic hydrocarbon group that includes a ring within the structure" within the description of the divalent linking group for R 0 $_{-}$1 . 

Specific examples of the alicyclic hydrocarbon group include groups in which two or more hydrogen atoms have been removed from cyclopentane, cyclohexane, norbomane, isobornane, adamantane, tricyclodecane and tetracyclodode› cane. 2 

When Y is a divalent linking group containing a hetero atom, preferred examples of the divalent linking group include -0-, ----C(=O)-O-, ----C(=O)-, -O----C (=0)-0-, ----C(=O)-NH-, -NH- (wherein H may be substituted with a substituent such as an alkyl group or acyl group), -S-, -S(=O) 2 -, -S(=O) 2 ---0-, and groups represented by general formulas -Y 21 ---0-Y 22 -[Y2l_C(=O)---0Jm-Y22_ and _y21_O----C (=O)-Y 22 - [wherein each ofY 21 and Y 22 independently represents a divalent hydrocarbon group which may have a substituent, 0 represents an oxygen atom, and m’ represents an integer of Oto 3]. 2 

When Y represents -NH-, the H may be substituted with a substituent such as an alkyl group or acyl group. The substituent (the alkyl group or acyl group or the like) prefer› ably contains 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and most preferably 1 to 5 carbon atoms. 21 22 21 

In the formulas -Y ---0-Y -, -[Y -C(=O)- 0]m-Y22- and-Y 21 -O----C(=O)-Y 22 -, each ofY 21 and Y 22 independently represents a divalent hydrocarbon group which may have a substituent. Examples of this diva› lent hydrocarbon group include the same groups as those described above for the "divalent hydrocarbon group which may have a substituent" for R 0 $_{-}$1 . Y 21 is preferably a linear aliphatic hydrocarbon group, more preferably a linear alky› lene group, still more preferably a linear alkylene group of 1 to 5 carbon atoms, and most preferably a methylene group or ethylene group. 22 

Y is preferably a linear or branched aliphatic hydrocar› bon group, and is more preferably a methylene group, ethyl- 

ene group or alkylmethylene group. The alkyl group within the alkylmethylene group is preferably a linear alkyl group of 1 to 5 carbon atoms, more preferably a linear alkyl group of 1 to 3 carbon atoms, and most preferably a methyl group. 

In the group represented by formula -[Y 21 ----C(=O)- OJm -Y 22 -, m’ represents an integer of Oto 3, and is pref› erably an integer of 0 to 2, more preferably 0 or 1, and most preferably 1. In other words, the group represented by for› mula -[Y 21 ----C(=O)-Olm-Y 22 - is most preferably a group represented by a formula -Y 21 ----C(=O)-O› Y22 -. Among such groups, groups represented by -(CH 2 )a,C(=O)---O-(CH 2 )$_{6}$ ,-areparticularlypreferred. In this formula, a’ represents an integer of 1 to 10, preferably an integer of 1 to 8, more preferably an integer of 1 to 5, still more preferably 1 or 2, and most preferably 1. b’ represents an integer of 1 to 10, preferably an integer of 1 to 8, more preferably anintegerofl to 5, still more preferably 1 or 2, and most preferably 1. 

The divalent linking group containing a hetero atom for Y 2 is preferably an organic group composed of a combination of at least one non-hydrocarbon group and a divalent hydrocar› bon group. Among such groups, linear groups containing an oxygen atom as the hetero atom, such as groups containing an ether linkage or an ester linkage, are preferred, a group rep› resented by one of the above formulas -Y 21 -O-Y 22 -, -[Y21----C(=O)---O]m-Y22_ or _y21_O----C(=O)- Y22 - is more preferred, and a group represented by the formula -[Y 21 ----C(=O)---0]m-Y 22 - or the formula -Y 21 -O----C(=O)-Y 22 - is particularly desirable. 

Among the above possibilities, Y 2 is preferably a linear or branched alkylene group, or a divalent linking group contain› ing a hetero atom, and is more preferably a linear or branched alkylene group, a group represented by the above formula -Y 21 -O-Y 22 -, a group represented by the above for› mula -[Y 21 ----C(=O)-Olm - Y 22 -or a group represented by the above formula -Y 21 ---0-C(=O)-Y 22 -. 

Specific examples of the structural unit (al 1) include struc› tural units represented by general formulas (al-1) to (al-4) shown below. 

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