A semiconductor device has a semiconductor substrate including an n-type high impurity concentration layer inhibiting a depletion layer from spreading, an n-type low impurity concentration drift layer, and a p-type high impurity concentration layer forming a p-n main junction between the drift layer. In the active region, an effective current flows in the direction of the thickness of the substrate. The device has an inclined trench that cuts the p-n main junction at a positive bevel angle from the semiconductor substrate surface on the side of the n-type high impurity concentration layer to penetrate through the substrate for separating it into chips. In the device, along the sidewall of the inclined trench in the n-type drift layer, an n-type surface region is formed with an impurity concentration lower than that in the n-type drift layer.