Resist material and patterning process

A resist material comprising a base polymer and an acid generator, wherein the resist material contains, as the acid generator, a sulfonium salt or iodonium salt of a sulfonic acid bonded to a maleimide group represented by the following general formula (A-1) or (A-2),

• wherein R1 and R2 each represent a hydrogen atom, a linear alkyl group having 1 to 10 carbon atoms, or a branched, or cyclic alkyl group having 3 to 10 carbon atoms, R1 and R2 optionally being bonded to each other to form a ring;
• X represents a divalent linking group containing an ester bond and having 1 to 20 carbon atoms, the linking group optionally containing an oxygen atom, a sulfur atom, a nitrogen atom, or a halogen atom;
• Rf11 to Rf14 each independently represent a hydrogen atom, a fluorine atom, an oxygen atom, a methyl group, or a trifluoromethyl group, provided that at least one of Rf11 to Rf14 is a fluorine atom or a trifluoromethyl group, and that when Rf11 and Rf12 are respectively an oxygen atom, Rf11 and Rf12 are a single oxygen atom bonded to a single carbon atom to form a carbonyl group;
• R3, R4, R5, R6, and R7 each independently represent a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, or a hydrocarbyl group having 1 to 25 carbon atoms and optionally containing a heteroatom, wherein the hydrocarbyl group is saturated or unsaturated and is linear, branched, or cyclic, some or all hydrogen atoms of these groups are optionally substituted with a hydroxy group, a carboxy group, a halogen atom, a cyano group, a nitro group, a mercapto group, a sultone group, a sulfonic group, or a sulfonium salt-containing group, and some carbon atoms of these groups are optionally substituted with an ether bond, an ester bond, a carbonyl group, an amide bond, a carbonate group, or a sulfonic acid ester group;
• and R3 and R4 are optionally bonded with each other to form a ring with a sulfur atom that is bonded thereto.