A semiconductor device 1 includes a square substrate 2, first RESURF structures 3 in the shape of planar stripes on an element area 10 of a main surface of the substrate 2, a transistor T arranged between the first RESURF structures 3, a first high withstand voltage section 11 constituted by second RESURF structures 3a in the shape of planar strips on a periphery of the main surface of the substrate 2, and a second high withstand voltage section 12 constituted by third RESURF structures 3b which are symmetrically arranged at corners of the substrate 2 with respect to a diagonal line D of the main surface of the substrate 2.