A method includes anisotropically etching an etching target layer of a target object through an opening of the target object by generating plasma of a first gas within a processing vessel in which the target object is accommodated; and then forming a film on an inner surface of the opening by repeating a sequence comprising: a first process of supplying a second gas into the processing vessel; a second process of purging a space within the processing vessel; a third process of generating plasma of a third gas containing an oxygen atom within the processing vessel; and a fourth process of purging the space within the processing vessel. The first gas contains a carbon atom and a fluorine atom. The second gas contains an aminosilane-based gas. The etching target layer is a hydrophilic insulating layer containing silicon. Plasma of the first gas is not generated in the first process.