Jan. 13,  2011  9  US 2011/0008728 Al  [0141]  Specific examples of the structural unit (al) include  structural units represented by general formulas (al-1) to  (al-4) shown below.  [Chemical Formula 9]  (al-1)  (al-2)  [Chemical Formula 10]  (al-1-1)  (al-3)  (al-1-2)  (al-4)  (al-1-3)  (al-1-4)  In the formulas, X 1  represents a tertiary alkyl ester-type acid  dissociable, dissolution inhibiting group; Y represents an  alkyl group of 1 to 5 carbon atoms or an aliphatic cyclic  group; n represents an integer of O to 3; Y 2  represents a  divalent linking group; R is the same as defined above; and  each ofR $^{11 }$and R $^{21 }$independently represents a hydrogen atom  or an alkyl group of 1 to 5 carbon atoms.  [0142]  Examples of the tertiary alkyl ester-type acid disso› ciable, dissolution inhibiting group for X 1  include the same  tertiary alkyl ester-type acid dissociable, dissolution inhibit› ing groups as those described above for X  1 .  [0143]  As R 11 , R 21 , n and Y are respectively the same as  defined for R  11 , R  21 , n and Y in general formula  (p  1) described  above in connection with the "acetal-type acid dissociable,  dissolution inhibiting group".  [0144]  As examples of Y 2 ,  the same groups as those  described above forY 2  in general formula (al-0-2) can be  given.  [0145]  Specific examples of structural units represented by  general formula (al-1) to (al-4) are shown below.  [0146]  In the formulas shown below, R"’ represents a hydro› gen atom, a methyl group or a trifluoromethyl group.  k H2  c,.._I  C  I  O=C  \ $_{0 }$ I  X’ 