An etching method includes loading a target substrate W into a chamber 40, the target substrate W having a silicon nitride film formed thereon and at least one of a polysilicon film and a silicon oxide film formed adjacent to the silicon nitride film; supplying a fluorine (F)-containing gas and an O2 gas into the chamber 40, while at least the O2 gas is excited; and selectively etching the silicon nitride film with respect to at least one of the polysilicon film and the silicon oxide film using the F-containing gas and the O2 gas.