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(In the formula, each R $^{9 }$independently represents a hydro- gen atom, a fluorine atom, a methy 1 group or a trifluoromethy 1 group; X 1 represents an acid-labile group; G represents an oxygen atom or a carbonyloxy group (-C(=O)O-).) 

As above, the polymer of the present invention can further include any one or more kinds of repeating units represented by the foregoing general formulae (11) to (15) in addition to a repeating unit represented by the foregoing general formula ( 4), preferably a repeating unit represented by the foregoing general formula (5). 

Further, the present invention provides a method for pro› ducing a polymer, wherein at least, the polymer is obtained by copolymerizing a monomer represented by the following general formula (2-1) and a monomer represented by the following general formula (2-2). 

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-continued 

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(In the formula, xa- represents a non-nucleophilic anion; za+ represents a lithium ion, a sodium ion, a potassium ion, an ammonium ion, an iodonium ion or a sulfonium ion; R 4 , R 5 , R 11 , R 21 , R 31 , W 1 , W$^{2}$,A 1 , p, q, k, mandnrepresentthe same as before.) 

As above, in the case that a monomer represented by the foregoing general formula (2-1) and a monomer represented by the foregoing general formula (2-2) are copolymerized, there exist two kinds of anions and two kinds of cations mixedly in the polymer matrix, and thus it is considered that an onium salt formed of a combination of the cation in the general formula (2-1) and the anion in the general formula (2-2) can exist. That is, a polymer including a repeating unit represented by the foregoing general formula ( 4) can be obtained by copolymerizing a monomer represented by the foregoing general formula (2-1) and a monomer represented by the foregoing general formula (2-2). 

Further, the present invention provides a method for pro- ducing a polymer, wherein the polymer is obtained by blend› ing a polymer containing a repeating unit represented by the following general formula (2-1 )’ and a polymer containing a repeating unit represented by the following general formula (2-2)’. 

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