A method of forming an ion implantation mask includes forming a field area on a semiconductor substrate, forming an amorphous carbon layer on the semiconductor substrate, forming a hard mask layer on the amorphous carbon layer, forming an etching mask pattern on the hard mask layer, and etching the hard mask layer and the amorphous carbon layer to expose the field area through the etching mask pattern, wherein etching the hard mask layer and the amorphous carbon layer forms a hard mask layer pattern and an amorphous carbon layer pattern.