PURPOSE: To effectively suppress a discharge by concentrating an electric field by forming a groove by etching on the main surface of a semiconductor, further etching the entirety to the specific depth, thereby forming the shape deleted at the corners of the portion crossing with the sides of the groove at the main surface.

CONSTITUTION: A substrate 7 is formed of N tupe silicon, an impurity layer 8 is formed by diffusing P type impurity, oxidized films, 9, 10 are, for example, formed of a silicon oxide film, and a pattern is formed on the film 9. When etching is conducted, a groove 12 is formed, and the films 9, 10 are moved, the groove 12 corresponds to the pattern of the film 9. When the wafer is further etching in approx. 5∼10μm, the portion 8a that the side of the groove 12 and the main surface cross is removed at the corners to concentrate the electric field, thereby forming a round corner. Then, a protective film 13 is formed on the surface of the groove 12, electrode layers 14, 15 are respectively formed on the layer 8 and the substrate 7. When the wafer is cut along the line A-A', a plurality of chip for forming diodes are obtained.