Semiconductor device

A semiconductor device, comprising:

• a first insulating film;
• a semiconductor part provided on the first insulating film, the semiconductor part including a bottom surface and an upper surface, the bottom surface contacting the first insulating film, the upper surface being at a side opposite to the bottom surface;
• and
• a second insulating film surrounding the semiconductor part, the second insulating film filling a trench provided around the semiconductor part, the trench extending from the upper surface of the semiconductor part toward the first insulating film and reaching the first insulating film,
• the semiconductor part including first to fourth semiconductor layers and first to third contact regions, the first and fourth semiconductor layers being of a first conductivity type, the second and third semiconductor layers being of a second conductivity type, the first and second contact regions being of the second conductivity type, the third contact region being of the first conductivity type,
• the first semiconductor layer extending along the first insulating film and contacting the second insulating film,
• the second to fourth semiconductor layers being provided on the first semiconductor layer and arranged in a first direction along the upper surface of the semiconductor part, the fourth semiconductor layer being provided between the second semiconductor layer and the third semiconductor layer, the second and third semiconductor layers each contacting the second insulating film,
• the first semiconductor layer extending between the second semiconductor layer and the fourth semiconductor layer and between the third semiconductor layer and the fourth semiconductor layer, the fourth semiconductor layer being apart from the second and third semiconductor layers with the first semiconductor layer interposed at the upper surface of the semiconductor part,
• the first contact region being provided on the second semiconductor layer,
• the second contact region being provided on the third semiconductor layer,
• the third contact region being provided on the fourth semiconductor layer,
• the first and second contact regions each including a second-conductivity-type impurity with a higher concentration than a concentration of a second-conductivity-type impurity in the second semiconductor layer and a concentration of a second-conductivity-type impurity in the third semiconductor layers,
• the fourth semiconductor layer including a first-conductivity-type impurity with a higher concentration than a concentration of a first-conductivity-type impurity in the first semiconductor layer,
• the third contact region including a first-conductivity-type impurity concentration with a higher concentration than the concentration of the first-conductivity-type impurity in the fourth semiconductor layer,
• the first to third contact regions extending in a second direction along the upper surface of the semiconductor part, the second direction crossing the first direction, the first to third contact regions being apart from the second insulating film,
• the first and second contact regions being provided with first distances in the second direction to the second insulating film, the first distances being less than a second distance in the second direction from the third contact region to the second insulating film.