Semiconductor device and method of manufacturing semiconductor device

A method of manufacturing a semiconductor device having an active region, comprising:

• forming in a semiconductor substrate, a first conductivity type region, and a second conductivity type region on the first conductivity type region, thereby forming a pn junction between the first conductivity type region and the second conductivity type region, the pn junction extending outwardly from the active region;
• forming farther outward than the active region, a trench having a width extending in a first direction, and a predetermined depth extending in a second direction, and away from a first principal surface of the semiconductor substrate, the trench terminating the pn junction;
• forming a first insulating film over the first principal surface of the semiconductor substrate, the first insulating film being embedded in the trench so as to leave a groove having a U-shape in cross-sectional view;
• selectively removing the first insulating film at the active region, to form a contact hole, and to expose the first principal surface of the semiconductor substrate in the contact hole;
• forming a metal film along the first principal surface of the semiconductor substrate exposed in the contact hole, and along an interior wall of the groove;
• selectively removing portions of the metal film, leaving a first remaining portion of the metal film and a second remaining portion of the metal film, the first and second remaining portions extending from the first principal surface of the semiconductor substrate exposed in the contact hole to the interior wall of the groove, the first remaining portion on the first principal surface of the semiconductor substrate being the first electrode, the second remaining portion at the interior wall of the groove being the first field plate;
• and
• embedding in the trench, a second insulating film so as to cover the first field plate.