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[0062] Non-Patent Document 1 points out that the decom› position of an acid generator, typically triphenylsulfonium salt is provoked not only by light exposure, but also with radicals. This suggests that the resist material is improved in sensitivity if many radicals generate upon light exposure. 

[0063] An iodized or brominated hydrocarbyl group (ex› clusive of aromatic ring in which iodine or bromine substi› tutes on a carbon atom) generates radicals upon EUV exposure. The aromatic ring having iodine or bromine bonded thereto is stable enough to generate no radicals upon EUV exposure, whereas iodine or bromine bonded to a carbon atom other than a carbon atom on aromatic ring is detached upon EUV exposure, to generate radicals. The radicals promote decomposition of an acid generator to bring an increase of sensitivity. 

[0064] The recurring unit (a) functions as a quencher due to the structure of an ammonium salt of an iodized or brominated carboxylic acid. In this sense, the base polymer may be referred to as a quencher-bound polymer. The quencher-bound polymer has the advantages of a remarkable acid diffusion-suppressing effect and improved resolution. In addition, since the recurring unit (a) contains iodine atom having great photo-absorption or bromine atom having a high electron generation efficiency, it generates secondary electrons or radicals to promote decomposition of the acid generator during exposure, leading to a high sensitivity. As a result, a high sensitivity, high resolution, and low LWR or improved CDU are achieved at the same time. 

[0065] Iodine or bromine is less soluble in alkaline devel› oper because of a relatively large atomic weight. When iodine or bromine is attached to the polymer backbone, a resist film in the exposed region is reduced in alkaline solubility, leading to losses of resolution and sensitivity and causing defect formation. When the recurring unit (a) is in an alkaline developer, the iodized or brominated carboxylic 

