Disclosed is a photosensitive polymer comprising pentafluoromethylvinyl ether derivative monomer having the formula: wherein R may be an alkoxy carbonyl, alkylsilane, a fluorine-substituted or unsubstituted C3–C20 alkyl carbonyl, a fluorine-substituted or unsubstituted C3–C20 cycloalkylcarbonyl or a fluorine-substituted or unsubstituted benzoyl substituent group. The photosensitive polymer is the polymerization product of the pentafluoromethylvinyl ether derivative monomer and at least one additional monomer selected from the group consisting of (meth)acrylic acid, (meth)acrylate, styrene, norbornene, tetrafluoroethylene and maleic anhydride monomers. The photosensitive polymer may be used in photoresist compositions for exposure light sources having a predominant wavelength of less than 157 nm.