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

A silicon carbide semiconductor device, comprising:

• a semiconductor substrate containing silicon carbide, the semiconductor substrate having a first main surface and a second main surface that are opposite to each other;
• a first semiconductor region of a first conductivity type, provided in the semiconductor substrate;
• a second semiconductor region of a second conductivity type, provided in the semiconductor substrate and between the first main surface of the semiconductor substrate and the first semiconductor region;
• a plurality of third semiconductor regions of the first conductivity type, selectively provided in the semiconductor substrate and between the first main surface of the semiconductor substrate and the second semiconductor region;
• a plurality of trenches including a plurality of first trenches and a plurality of second trenches different from each other, the plurality of first trenches penetrating through the plurality of third semiconductor regions and the second semiconductor region and reaching the first semiconductor region, the plurality of second trenches being provided apart from the plurality of third semiconductor regions, penetrating through the second semiconductor region and reaching the first semiconductor region;
• a plurality of gate electrodes respectively provided in the plurality of first trenches, via a plurality of gate insulating films;
• a plurality of conductive films respectively embedded in the plurality of second trenches, each of the plurality of conductive films being configured by a plurality of stacked metal films made of materials different from one another, junction interfaces between the first semiconductor region and the plurality of conductive films forming a plurality of Schottky barriers;
• a first electrode electrically connected to the second semiconductor region, the plurality of third semiconductor regions, and the plurality of conductive films, the first electrode including an aluminum film or an aluminum alloy film;
• a second electrode provided at the second main surface of the semiconductor substrate;
• and
• a plurality of Schottky barrier diodes that respectively include the plurality of Schottky barriers, wherein
• each of the plurality of conductive films has:
• a first metal film provided along an inner wall of a respective one of the plurality of second trenches, the first metal film being in Schottky contact with the first semiconductor region, at the inner wall of the respective one of the plurality of second trenches, and
• a second metal film provided closer to a center of the respective one of the plurality of second trenches than is the first metal film, the second metal film having an electrical resistivity that is lower than an electrical resistivity of the first metal film,
• the first metal film is a nickel film,
• the second metal film is a tungsten film, and
• the first metal film has:
• a first portion at a bottom of the respective one of the plurality of second trenches, and
• a second portion at a sidewall of the respective one of the plurality of second trenches,
• a thickness of the second portion being smaller than a thickness of the second metal film.