Bis{4-[2＇-[vinyloxy)ethoxy]phenyl}-4-methoxyphenylsulfonium triflate (TPS-2VE-Tf) and tris{4-[2＇-(vinyloxy)ethoxy]phenyl}sulfonium triflate (TPS-3VE-Tf) were synthesized as thermally crosslinkable photoacid generators (PAGs) and used in a two-component chemically amplified photoresist system. The photoresist films formulated with poly(p-hydroxystyrene) (PHS) as a binder polymer and a thermally crosslinkable PAG are insolubilized in aqueous base by prebaking due to the thermal crosslinking reaction between PHS and the PAG. The insolubilization temperature of the resists and conversion of vinyl ether groups are greatly influenced by the PAG concentration and prebaking temperature, respectively. Upon exposure to deep UV and subsequent postexposure bake, the crosslinks are cleaved by photogenerated acid, leading to effective solubilization of the exposed areas. Photoresists containing TPS-2VE-Tf and TPS-3VE-Tf exhibited sensitivities of 12 and 45 mJ/cm(2), respectively. Positive-tone images were obtained using a 2.38 wt% aqueous tetramethyl-ammonium hydroxide developer.