A semiconductor device includes a substrate having a main surface inclined in an off-direction from a {0001} surface, a semiconductor layer, and an epitaxial layer. The semiconductor layer includes a trench. Where an upstream side is an off-angle upstream side and a downstream side is an off-angle downstream side in a direction with the off-direction projected on the main surface of the substrate, a side wall of the trench includes first and second side wall portions facing each other and each crossing the off-direction of the substrate. The first side wall portion is situated closer to the off-angle upstream side than the second side wall portion.