A semiconductor device includes: a first semiconductor region; a second semiconductor region; a third semiconductor region; a fourth semiconductor region; an insulation film, which is arranged on an inner wall of a recess that extends from an upper surface of the fourth semiconductor region and reaches the second semiconductor region with penetrating the fourth semiconductor region and the third semiconductor region; a control electrode, which is arranged on the insulation film on a side surface of the recess and faces the third semiconductor region; a first main electrode, which is electrically connected to the first semiconductor region, and a second main electrode, which is electrically connected to the fourth semiconductor region, wherein a ratio of a width of the recess to a width of the third semiconductor region contacting the second main electrode is 1 or larger.