PROBLEM TO BE SOLVED: To provide an etching method which enables etching of a SiN film with a high selection ratio against an SiOfilm and/or a poly-Si film.SOLUTION: An etching method comprises: arranging a processed substrate W which has a silicon nitride film on a surface and a polysilicon film and/or a silicon oxide film which are provided adjacent to the silicon nitride film in a chamber 40; supplying an NO gas or/and an ozone gas and an HF gas to inside the chamber 40; and selectively etching the silicon nitride film.
