Method of forming thick resist pattern

(Amended) A method of forming a thick film resist pattern using a photoresist film having a film thickness of 2.0 μm or more, wherein a radiation sensitive resin composition comprises an alkali-soluble resin and a photosensitizer containing a quinone diazide group, and said alkali-soluble resin is a mixture of a novolak resin and one or more resins selected from the group consisting of a homopolymer or a copolymer comprising two or more monomer units selected from the group of methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, n-hexyl acrylate, isopropyl acrylate, isobutyl acrylate, t-butyl acrylate, cyclohexyl acrylate, benzyl acrylate, 2-chloroethyl acrylate, methyl-α-chloroacrylate, phenyl α-bromoacrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, n-hexyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, phenylmethacrylate, 1-phenylethylmethacrylate, 2-phenylethyl methacrylate, furfuryl methacrylate, diphenylmethyl methacrylate, pentachlorophenyl methacrylate, naphthyl methacrylate, iso-boronyl methacrylate, benzyl methacrylate, 4-fluorostyrene, 2,5-difluorostyrene, 2,4-difluorostyrene, p-isopropylstyrene, styrene, o-chlorostyrene, 4-acetylstyrene, 4-bezoylstyrene, 4-bromostyrene, 4-butoxycarbonylstyrene, 4-butoxymethylstyrene, 4-butylstyrene, 4-ethylstyrene, 4-hexylstyrene, 4-methoxystyrene, 4-methylstyrene, 2,4-dimethylstyrene, 2,5-dimethylstyrene, 2,4,5-trimethylstyrene, 4-phenylstyrene, 4-propoxystyrene.