Photosensitive polymer and chemically amplified photoresist composition containing the same

The photosensitive polymer includes a first monomer which is norbornene ester having C₁ to C₁₂ aliphatic alcohol as a substituent, and a second monomer which is maleic anhydride. A chemically amplified photoresist composition, containing the photosensitive polymer, has an improved etching resistance and adhesion to underlying layer materials, and exhibits wettability to developing solutions.