An insulating film (2) is formed on a main surface of a semiconductor substrate (1) that includes an active region and a termination region. The insulating film (2) in the active region is etched to form an opening (3). The insulating film (2) is used as a mask and an impurity is implanted into the semiconductor substrate (1) in a direction tilted by 20° or more from a direction normal to the main surface of the semiconductor substrate (1) while rotating the semiconductor substrate (1) to form a diffusion layer (7) in the active region. The diffusion layer (7) extends wider than the opening (3) up to below the insulating film (2) on the termination region side.