To suppress stress variation on a channel forming region, a semiconductor device includes an element isolating region on the semiconductor substrate principal surface, and an element forming region on the principal surface to be surrounded by the element isolating region. The principal surface has orthogonal first and second directions. A circumferential shape of the element forming region has a first side extending along the first direction. The element forming region has a first transistor region (TR1), a second transistor region (TR2) arranged between the first side and TR1, and a dummy region on the first direction side of TR1. TR1 has a first channel forming region facing the first side. TR2 has a second channel forming region facing the first side. The first channel forming region has a non-facing region that is not facing the second channel forming region. The dummy region faces the non-facing region in the second direction.