(al-0-13)  (al-0-2)  In the above formulas, R represents a hydrogen atom, an alkyl  group of 1 to 5 carbon atoms or a halogenated alkyl group of  1 to 5 carbon atoms, R$^{21 }$represents an alkyl group, R$^{22 }$rep- resents a group that forms an aliphatic monocyclic group  together with the carbon atom to which R$^{22 }$is bonded, R 23  represents a branched alky 1 group, R $^{24 }$represents a group that  forms an aliphatic polycyclic group together with the carbon  atom to which R$^{24 }$is bonded, R$^{25 }$represents a linear alkyl  group of 1 to 5 carbon atoms, Y$^{2 }$represents a divalent linking  group, and X $^{2 }$represents an acid-dissociable group.  In each of the above formulas, R, Y$^{2 }$and X$^{2 }$are the same as  defined above.  In formula (al-0-11), examples of the alkyl group for R 21  include the same alkyl groups as those described above for  R $^{14 }$in the formulas (1-1) to (1-9), and a methyl group, ethyl  group or isopropyl group is preferred.  In terms of R 22 , examples of the aliphatic monocyclic  group that is formed together with the carbon atom to which  R 22  is bonded include the monocyclic groups among the  aliphatic cyclic groups described above in connection with  the tertiary alkyl ester-type acid-dissociable groups. Specific  examples include groups in which one or more hydrogen  atoms have been removed from a monocycloalkane. The  monocycloalkane is preferably a 3- to I I-membered ring,  more preferably a 3- to 8-membered ring, still more prefer› ably a 4- to 6-membered ring, and most preferably a 5- or  6-membered ring.  A portion of the carbon atoms that constitute the ring of the  monocycloalkane may or may not be substituted with an ether  group (---0-).  Further, the monocycloalkane may include an alkyl group  of 1 to 5 carbon atoms, a fluorine atom, or a fluorinated alkyl  group of 1 to 5 carbon atoms as a substituent.  Examples of the R$^{22 }$group that constitutes the aliphatic  monocyclic group include linear alkylene groups which may  have an ether group  (-0-)  interposed between the carbon  atoms of the alkylene chain.  Specific examples of the structural units represented by  formula (al-0-11) include structural units represented by the  above formulas (al-1-16) to (al-1-23), (al-1-27) and (al-1- 31). Among these, structural units represented by general  formula ( al-1-02) shown below, which includes the structural  The present invention preferably includes, as the structural  unit ( al 1 ), at least one structural unit selected from the group  consisting of structural units represented by general formula  (al-0-11) shown below, structural units represented by gen› eral formula (al-0-12) shown below, structural units repre› sented by general formula (al-0-13) shown below, and struc› tural units represented by general formula (al-0-2) shown  below. Among these structural units, at least one structural  unit selected from the group consisting of structural units  represented by formula (al-0-11), structural units repre› sented by formula (al-0-12) and structural units represented  by general formula (al-0-2) is particularly desirable.  -continued  -continued  66  US  9,104,101 B2  65  (al-4-15)  (al-0-11)  (al-0-12)  [Chemical Formula 23] 