Disclosed herein are a top anti-reflective coating polymer used in a photolithography process, which is one of the fabrication processes for a semiconductor device, a method for preparing the anti-reflective coating polymer, and an anti-reflective coating composition comprising the anti-reflective coating polymer. Specifically, the top anti-reflective coating polymer is used in immersion lithography for the fabrication of a sub-50 nm semiconductor device. The top anti-reflective coating polymer is represented by Formula 1 below: ##STR00001## wherein R1, R2 and R3 are independently hydrogen or a methyl group; and a, b and c represent the mole fraction of each monomer, and are in the range between about 0.05 and about 0.9. Since a top anti-reflective coating formed using the above anti-reflective coating polymer is not soluble in water, it can be applied to immersion lithography using water as the medium for a light source. In addition, since the top anti-reflective coating can reduce the reflectance from an underlayer, the uniformity of CD is improved, thus enabling the formation of an ultrafine pattern.