A semiconductor device includes a transistor that has a trench formed in an element forming region of a substrate, a gate insulating film formed on side faces and a bottom face of the trench, a gate electrode formed on the gate insulating film so as to bury the trench, a source region formed on one side in the gate longitude direction, which is formed on the surface of the substrate, and a drain region formed on the other side in the gate longitude direction. Here, the gate electrode is formed so as to be exposed also on the substrate outside the trench, and the gate electrode is disposed so as to cover upper portions of both ends of the trench and so as to form at least one concave portion having a depth reaching the substrate in a center portion.