PURPOSE: To expand the effective area of a semiconductor substrate and to reduce ON-resistance by a method wherein a source bonding pad region, which is used common with a unit cell, is provided in advance on one surface of a semiconductor substrate, and a plurality of unit cell regions and a prober region, having the area two or three times the unit cell region, are provided on the part directly under the source bonding pad region.

CONSTITUTION: A plurality of unit cell regions 8 and a P+ diffusion region 9, having the area two to three times the unit cell region 8, are formed on the semiconductor substrate located directly under a source bonding pad region which is provided in advance. A part of the source bonding pad is used as a P+ prober region and other part is used as an effective part which works as a MOSFET. The P+ area is formed larger than a flaw caused by a probing needle, and the wafer damage, caused when current and voltage between the source and drain are tested in the manufacturing process by bringing a probing needle into contact with an electrode part to check and select the characteristics of each cell and the like in a diffusion process and the like, is prevented.