Abstract: A substrate processing method, involving etching a silicon nitride layer selectively in a substrate where a silicon oxide layer and the silicon nitride layer are stacked, includes: wet-etching the silicon nitride layer with a phosphoric acid-based etching solution; and dry-etching a regrowth oxide, which is formed on a surface of the silicon oxide layer in the wet etching step, with an etching gas.

Abstract: A method of processing a substrate on which films comprising a first silicon oxide film, a silicon nitride film and a second silicon oxide film are stacked from an outermost side, includes: a first etching step of etching the first silicon oxide film; and a second etching step of etching the silicon nitride film and the second silicon oxide film. In the first etching step, a residual layer of the first silicon oxide film is left. In the second etching step, the residual layer of the first silicon oxide film, the silicon nitride film and the second silicon oxide film are etched together.