Abstract: A method of forming a photoresist pattern having a uniformly fine line width, and a method of manufacturing a semiconductor device using such a photoresist pattern as a mask, include the step of forming an anti-reflective coating (ARC) using only a hydrocarbon based gas. A highly reflective layer is formed on a semiconductor substrate on which an underlayer is disposed. Using only a hydrocarbon based gas, the ARC is formed on the highly reflective layer. A photoresist layer is formed on the ARC, and is exposed and developed to form a photoresist pattern on the ARC. The ARC and the highly reflective layer under the photoresist pattern are etched using the photoresist pattern as a mask. Thereafter, the photoresist pattern and the ARC are simultaneously removed. The ARC is of an amorphous silicon film having high etching selectivity and being easily removed along with the photoresist pattern.