Method of removing silicon oxide film

A method of removing a silicon oxide film of a workpiece having an insulating film and the silicon oxide film exposed at a bottom portion of an opening formed in the insulating film, comprising:

• forming a protective film containing carbon on a surface of the workpiece, wherein the protective film has a first region extending along a side wall surface of the insulating film that defines the opening and a second region extending on the silicon oxide film;
• removing the second region of the protective film and the silicon oxide film by sputter etching with ions from plasma of a first inert gas;
• and
• removing a residue of the silicon oxide film by chemical etching,
• wherein forming a protective film is executed in a state where the workpiece is disposed in a chamber, and
• wherein forming a protective film includes:
• executing a plurality of cycles, each of the cycles including:
• forming a precursor layer containing carbon on the surface of the workpiece by supplying a carbon-containing gas into the chamber;
• purging the chamber;
• reducing the amount of impurities contained in the precursor layer by generating plasma of a second inert gas in the chamber;
• and
• purging the chamber.