A method of producing a semiconductor device includes forming an insulating film on a substrate on which a semiconductor layer is formed; removing a part of the insulating film by etching to form an opening in the insulating film; supplying steam with a temperature greater than or equal to 200° C. and less than or equal to 600° C. to the opening formed in the insulating film; after supplying the steam, applying a solution including a silicon compound to a side surface of the insulating film defining the opening; and forming a hydrophobic film on the side surface of the insulating film defining the opening by polymerizing the silicon compound.