Silicon carbide semiconductor device and method of manufacturing silicon carbide semiconductor device

A method of manufacturing a silicon carbide semiconductor device having on a front surface side of a semiconductor substrate, an element structure that has a predetermined semiconductor region provided in the semiconductor substrate and a protrusion protruding from a front surface of the semiconductor substrate, the method comprising:

• forming in the semiconductor substrate, the predetermined semiconductor region constituting the element structure;
• forming on a front surface of the semiconductor substrate, the protrusion constituting the element structure;
• stacking sequentially on the front surface of the semiconductor substrate, a first insulating film covering the element structure and a second insulating film covering the first insulating film, and forming an interlayer insulating film having a 2-layer structure constituted by the first insulating film and the second insulating film;
• performing heat treatment and planarizing a surface of the interlayer insulating film;
• partially removing the interlayer insulating film after planarizing the surface of the interlayer insulating film, and forming a contact hole that penetrates the interlayer insulating film in a depth direction and reaches the semiconductor substrate;
• and
• forming an electrode on the surface of the interlayer insulating film, embedding the electrode in the contact hole, and electrically connecting the semiconductor region and the electrode, wherein
• forming the interlayer insulating film includes:
• forming a non-doped silicon oxide film as the first insulating film, and
• forming an oxide film containing boron and phosphorus, as the second insulating film, and
• the second insulating film has a boron concentration in a range from 4.5 mol % to 8.0 mol %.