A photosensitive polymer, the photosensitive polymer including repeating units represented by Formulae 1 to 3: wherein R1 and R3 are independently hydrogen or methyl, R2 is a C4 to C20 acid-labile group, R4 is a lactone-derived group, AR is a substituted or unsubstituted phenyl ring, or a substituted or unsubstituted aryl having from two to three fused aromatic rings, carbon CAR is bonded directly to an aromatic ring of AR, l, m, and n are positive integers, l/(l+m+n) is about 0.1 to about 0.5, m/(l+m+n) is about 0.3 to about 0.5, and n/(l+m+n) is about 0.1 to 0.4.