Semiconductor device and method of manufacturing semiconductor device

A semiconductor device, comprising:

• a semiconductor substrate having a first main surface and a second main surface opposite to each other;
• an insulating film provided on the semiconductor substrate;
• a polysilicon layer provided at the first main surface of the semiconductor substrate via the insulating film;
• a first-conductivity-type region and a second-conductivity-type region that are provided in the polysilicon layer and that are adjacent to each other in a direction parallel to the first main surface of the semiconductor substrate to form a pn junction therebetween, whereby a diode is formed by the pn junction;
• an interlayer insulating film provided at the first main surface of the semiconductor substrate, the interlayer insulating film covering the polysilicon layer;
• a first contact hole penetrating through the interlayer insulating film in a depth direction of the semiconductor device, the first contact hole having a first bottom end that reaches the polysilicon layer;
• a second contact hole penetrating through the interlayer insulating film in the depth direction, the second contact hole having a second bottom end that reaches the polysilicon layer;
• a first contact trench penetrating the polysilicon layer to be continuous from the first bottom end of the first contact hole in the depth direction, an outer periphery of the first contact trench being surrounded by the first-conductivity-type region;
• a second contact trench penetrating the polysilicon layer to be continuous from the second bottom end of the second contact hole in the depth direction, an outer periphery of the second contact trench being surrounded by the second-conductivity-type region;
• a first first-conductivity-type high-concentration region selectively provided in the polysilicon layer and being in contact with the first-conductivity-type region, so as to be in direct contact with a bottom, sidewalls or both the bottom and the sidewalls of the first contact trench, the first first-conductivity-type high-concentration region having an impurity concentration that is higher than an impurity concentration of the first-conductivity-type region;
• a first electrode embedded in the first contact hole and the first contact trench, and being in contact with the first first-conductivity-type high-concentration region;
• and
• a second electrode embedded in the second contact hole and the second contact trench, and being in contact with the second-conductivity-type region.