Etching method and etching apparatus

An etching apparatus, comprising:

• a processing container in which a substrate is accommodated and whose interior is configured to be exhausted, wherein the substrate includes a first film, a porous film and a second film formed therein, each of the first film and the porous film being exposed from a surface of the substrate and the second film being not exposed from the surface of the substrate by being coated with the porous film;
• a gas supply path configured to supply an etching gas having an etching property with respect to the first film and the second film from a gas source to the interior of the processing container;
• a reservoir provided in the gas supply path and configured to store the etching gas;
• and
• a valve provided downstream of the reservoir in the gas supply path and configured to be closed to increase a pressure of the interior of the processing container by the etching gas stored in the reservoir to the interior of the processing container and to be open to supply the etching gas stored in the reservoir to the interior of the processing container such that the first film among the first film and the second film is selectively etched.