An amorphous carbon film, which has excellent etching resistance and is capable of reducing reflectance when a resist film is exposed to light, is form. A method for manufacturing a semiconductor device includes forming an object film to be etched on a wafer, supplying a process gas containing a CO gas and an N2 gas into a processing container, forming an amorphous carbon nitride film from the supplied CO gas and N2 gas, forming a silicon oxide film on the amorphous carbon nitride film, forming an ArF resist film on the silicon oxide film, patterning the ArF resist film, etching the silicon oxide film by using the ArF resist film as a mask, etching the amorphous carbon nitride film by using the silicon oxide film as a mask, and etching the object film to be etched by using the amorphous carbon nitride film as a mask.