A method of manufacturing a semiconductor device, the method comprising:
- in a first process, forming a first semiconductor region of a second conductivity type on a second semiconductor region of a first conductivity type, thereby forming a semiconductor substrate having a first main surface and a second main surface, and forming at a first main surface side of the semiconductor substrate, an element structure having a pn junction between the first semiconductor region and the second semiconductor region;
- in a second process, forming on the first main surface of the semiconductor substrate, an interlayer insulating film covering the element structure, the second process including
- forming a first insulating film as the interlayer insulating film, on the first main surface of the semiconductor substrate, and
- forming a second insulating film as the interlayer insulating film, on the first insulating film, the second insulating film being formed from an insulation material having an etching rate faster than an etching rate of the first insulating film with respect to the aqueous solution;
- in a third process, forming on the interlayer insulating film, a resist film in which predetermined a predetermined portion is opened;
- in a fourth process, selectively removing the interlayer insulating film to form a first contact hole that selectively exposes the first main surface of the semiconductor substrate, by performing etching using the resist film as a mask;
- in a fifth process, removing the resist film;
- in a sixth process, removing a natural oxide film covering a portion of the first main surface of the semiconductor substrate exposed in the first contact hole, by performing wet etching using an aqueous solution containing hydrofluoric acid or a dilute hydrofluoric acid, the sixth process including
- forming a step at a side wall of the first contact hole, thereby forming a second contact hole having a lower portion disposed at the first insulating film and an upper portion disposed at the second insulating film, to increase in a step-like shape a width of the upper portion greater than a width of the lower portion in a direction parallel to the first main surface of the semiconductor substrate, the step being formed between the upper portion and the lower portion;
- in a seventh process, forming along an inner surface of the second contact hole, a first metal film having high adhesion with the semiconductor substrate and forming an ohmic contact with the semiconductor substrate;
- in an eighth process, embedding in the second contact hole, a second metal film on the first metal film;
- and
- in a ninth process, forming a first electrode on the interlayer insulating film and the second metal film, and electrically connecting the first electrode to the first semiconductor region, via the second metal film and the first metal film.