A spacer is formed on side and top portions of a photoresist pattern after a mask process is performed so that the spacer may be used as an etching mask. The spacer is formed using a polymer deposition layer which is a low temperature oxide or nitride that can be deposited on side and top portions of the photoresist pattern at 75˜220° C. after the mask process is performed. A method for manufacturing a semiconductor device includes forming a bottom anti-reflection coating film on an etch-target layer, patterning a photoresist layer formed on the bottom anti-reflection coating film, forming an insulation layer on a patterned photoresist layer and the bottom anti-reflection coating film, etching back the insulation layer to form a spacer on sidewalls of the patterned photoresist layer, and etching the bottom anti-reflection coating film and the etching target layer exposed by the spacer to form a fine pattern.