A method of manufacturing a semiconductor device includes forming an etch target layer on a substrate; forming an amorphous metal layer on the etch target layer, the amorphous metal layer comprising nitrogen between 15 atomic percentage (at %) and 25 at %; forming an amorphous metal hardmask by patterning the amorphous metal layer; and etching the etch target layer by using the amorphous metal hardmask as an etching mask.