Disclosed herein are a method of depositing a thin film and a method of manufacturing a semiconductor using the same, having high selectivity by increasing etching resistance while an extinction coefficient associated with anti-reflectivity is maintained low. The method of depositing a thin film according to the invention includes (a) depositing an carbon anti-reflective film on the bottom film of a substrate; and (b) adding a compound containing nitrogen (N), fluorine (F) or silicon (Si) to the surface or the inner portion of the carbon anti-reflective film, to deposit a thin film of a-C:N, a-C:F or a-C:Si, having high selectivity, to a thickness from 1 to 100 nm using an atomic layer deposition process. Therefore, an ultrathin film having etching resistance is formed on or in the carbon anti-reflective film and the density and compressive stress of the carbon anti-reflective film are increased, thus increasing etching selectivity.