Patterning process

A pattern forming process comprising the steps of applying a resist composition comprising a (meth)acrylate copolymer comprising both recurring units having an acid labile group-substituted carboxyl group and recurring units having a lactone ring, an acid generator, and an organic solvent onto a substrate, in a first heat treating step heat treating the composition to form a resist film, selectively exposing a region of the resist film to high-energy radiation to form an exposed region of the film and an unexposed region of the film, in a second heat treating step heat treating the resist film, and developing the exposed film with a developer consisting of 40 to less than 100% by weight of a first solvent selected from a first group consisting of methyl benzoate, ethyl benzoate, phenyl acetate, benzyl acetate, methyl phenylacetate, benzyl formate, phenylethyl formate, methyl 3-phenylpropionate, benzyl propionate, ethyl phenylacetate, 2-phenylethyl acetate, and a combination of two or more of the solvents listed in the first group, and the balance of a second solvent selected from a second group consisting of 2-heptanone, 2-hexanone, 3-hexanone, diisobutyl ketone, methylcyclohexanone, acetophenone, methylacetophenone, propyl acetate, butyl acetate, isobutyl acetate, amyl acetate, butenyl acetate, isoamyl acetate, propyl formate, butyl formate, isobutyl formate, amyl formate, isoamyl formate, methyl valerate, methyl pentenoate, methyl crotonate, ethyl crotonate, methyl lactate, ethyl lactate, propyl lactate, butyl lactate, isobutyl lactate, amyl lactate, isoamyl lactate, and a combination of two or more of the solvents listed in the second group, to form a pattern of negative tone wherein the exposed region of the film is not dissolved and the unexposed region of the film is dissolved.