Radiation-sensitive resin composition and pattern formation method

A radiation-sensitive resin composition comprising:

• a polymer comprising a structural unit (I) represented by a formula (1) and a structural unit different from the structural unit (I);
• a radiation-sensitive acid generator represented by a formula (α);
• and
• a solvent,
• wherein
• RK1 is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group,
• L1 is an alkanediyl group having 1 to 5 carbon atoms, and
• Rf1 is a fluorinated hydrocarbon group having 2 to 10 carbon atoms and 5 to 7 fluorine atoms,
• wherein
• RW is a monovalent organic group having 3 to 40 carbon atoms that contains a cyclic structure,
• Rfa and Rfb are each independently a fluorine atom or a fluorinated hydrocarbon group having 1 to 10 carbon atoms,
• R11 and R12 are each independently a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 10 carbon atoms, or a fluorinated hydrocarbon group having 1 to 10 carbon atoms,
• n1 is an integer of 1 to 4, when n1 is 2 or more, a plurality of Rfas are identical or different from each other, and a plurality of Rfbs are identical or different from each other,
• n2 is an integer of 0 to 4, when n2 is 2 or more, a plurality of R11s are identical or different from each other, and a plurality of R12s are identical or different from each other,
• no carbonyl group is present between a sulfur atom of the sulfonic acid ion and the cyclic structure of RW, and
• Z+ is a monovalent onium cation.