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N-substituted maleimide, acrylonitrile, methacrylonitrile, vinylnaphthalene, vinylanthracene, indene which may have a substituent, and a polymerizable monomer having an alcoholic hydroxyl group substituted with a fluoroalkyl group or the like at the a-position. Preferred examples of the substituted styrene include 4-(1-naphthylmethoxy)styrene, 4-benzyloxystyrene, 4-( 4-chlorobenzyloxy)styrene, 3-(1- naphthylmethoxy)styrene, 3-benzyloxy styrene, and 3-(4- chlorobenzyloxy)styrene. 

[0156] The polymer compound (A) may or may not con› tain such other repeating unit, but in the case of containing such other repeating unit, the content thereof in the polymer compound (A) is generally 1 mo! % to 20 mo! %, and preferably 2 mo! % to 10 mo! %, based on the total repeating units constituting the polymer compound (A). 

[0157] The polymer compound (A) can be synthesized, for example, by radical, cationic or anionic polymerization of unsaturated monomers corresponding to respective repeat› ing units. The polymer compound can be also synthesized by polymerizing a polymer from unsaturated monomers corre› sponding to precursors of respective repeating units, and modifying the synthesized polymer with a low molecular compound, thereby converting the precursors into desired repeating units, in either case, living polymerization such as living anionic polymerization is preferably used, because the obtained polymer compound can have a uniform molecular weight distribution. 

[0158] The weight average molecular weight of the poly› mer compound (A) is preferably 1,000 to 200,000, more preferably 2,000 to 50,000, and still more preferably 2,000 to 15.000. The polydispersity (molecular weight distribu› tion) (Mw/Mn) of the polymer compound (A) is, in view of sensitivity, preferably from 1.0 to 1.7, and more preferably from 1.0 to 1.2. The weight average molecular weight and the polydispersity of the polymer compound (A) are defined in terms of polystyrene by GPC measurement. 

[0159] In the present specification, the weight average molecular weight and polydispersity can be determined, for example using HLC-8120 (manufactured by Tosoh Corpo› ration), TSK gel Multipore HXL-M (manufactured by Tosoh Corporation, 7.8 mmIDx30.0 cm) as a colunm, and tetra› hydrofuran (THF) as an eluting solution. 

[0160] In the composition of the present invention, two or more of these polymer compounds (A) may be mixed and used. 

[0161] The content of the polymer compound (A) is preferably 30 mass % to 100 mass %, more preferably 50 mass% to 99.7 mass%, and particularly preferably 70 mass % to 99.5 mass %, based on the total solid content of the composition of the present invention. 

[0162] [2] (B) Compound Capable of Generating Acid Upon Irradiation with Actinic Rays or Radiation 

[0163] The actinic ray-sensitive or radiation-sensitive resin composition of the present invention further contains (B) a compound capable of generating an acid upon irra› diation with actinic rays or radiation (hereinafter, sometimes simply referred to as an "acid generator") as an essential component. In the present invention, the compound (B) capable of generating an acid upon irradiation with actinic rays or radiation may be a low-molecular weight acid generator capable of generation an acid upon irradiation with actinic rays or radiation (particularly an electron beam or extreme ultraviolet rays) or may be an acid-generating polymer compound. As described above, also preferred is an 

embodiment in which the compound (B) is integrated as one constituent component of the polymer compound (A), that is, the polymer compound (A) includes a repeating unit further containing a group capable of generating an acid upon irradiation with actinic rays or radiation in the main chain or side chain. 

[0164] A preferred aspect of the acid generator is an onium compound. Examples of the onium compound include a sulfonium salt, an iodonium salt, and a phosphonium salt. 

[0165] Another preferred embodiment of the acid genera› tor is a compound capable of generating a sulfonic acid, an imide acid, or a methide acid upon irradiation with actinic rays or radiation. Examples of the acid generator in this embodiment include a sulfonium salt, an iodonium salt, a phosphonium salt, oxime sulfonate, and imidosulfonate. 

[0166] The acid generator for use in the present invention is not limited to a low-molecular weight compound, and a compound where a group capable of generating an acid upon irradiation with actinic rays or radiation is introduced into the main or side chain of a polymer compound may also be used. Furthermore, in the case where, as described above, a group capable of generating an acid upon irradiation with actinic rays or radiation is present in a repeating unit serving as a copolymerization component of the polymer compound (A) for use in the present invention, the acid generator (B) as a molecule different from the polymer compound (A) of the present invention may be absent. 

[0167] The acid generator is preferably a compound capable of generating an acid upon irradiation with an electron beam or extreme ultraviolet rays. 

[0168] In the present invention, the onium compound is preferably a sulfonium compound represented by the fol› lowing General Formula (I) or an iodonium compound represented by General Formula (2). 

[0169] In General Formulae (1) and (2), 

[0170] Rau Ra$_{2}$ , Ra$_{3}$ , Ra$_{4}$ , and Ras each independently represent an organic group. 

[0171] x- represents an organic anion. 

[0172] Hereinafter, the sulfonium compound represented by General Formula (1) and the iodonium compound rep› resented by General Formula (2) will be described in more detail. 

[0173] Ra$_{1 }$to Ra$_{3 }$ in General Formula (1) and Ra$_{4 }$ and Ras in General Formula (2) each independently represent an organic group, but each of at least one of Ra$_{1}$ , Ra$_{2}$ , or Ra$_{3 }$ and at least one of Ra$_{4 }$ or Ras is preferably an aryl group. The aryl group is preferably a phenyl group or a naphthyl group, and more preferably a phenyl group. 

[0174] Examples of the organic anion of x- in General Formulae (1) and (2) include a sulfonate anion, a carboxy› late anion, a bis(alkylsulfonyl)amide anion, and a tris(alkyl› sulfonyl)methide anion. The organic anion is preferably an organic anion represented by the following General Formula 

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(1) 

(2) 

