Radiation-sensitive resin composition and pattern formation method

Provided are: a radiation-sensitive resin composition with which it is possible to form a resist film that is capable of exhibiting satisfactory levels of sensitivity, LWR performance, CDU performance, pattern rectangularity, and etching resistance; and a pattern formation method. This radiation-sensitive resin composition contains an onium salt compound represented by formula (1), a resin containing a structural unit having an acid-dissociable group, and a solvent. (In formula (1), R1 and R2 each independently are a hydrogen atom, a fluorine atom, or a C1-10 monovalent fluorinated hydrocarbon group. n is an integer of 0-3; when n is 2 or greater, the plurality of R1 and R2 are the same as or different from each other. L is a C3-40 divalent hydrocarbon group including a cyclic structure. R3 is a C1-40 monovalent organic group that does not have an acid-dissociable group. Z+ is a monovalent radiation-sensitive onium cation.).