POWER TRANSISTOR

PROBLEM TO BE SOLVED: To obtain a power transistor having the reduced invalid part and the high efficiency by providing a base diffused region even directly under an emitter bonding pad. SOLUTION: A pectinated part 24 is formed on a boundary between a base diffused region 22 and an emitter diffused region 23, and so formed at the emitter peripheral length of the part operated as a transistor is increased as compared with the surface area. A base electrode 26 on the surface of the region 22 is formed only above the part of the region 22 on the part 24, an emitter electrode 27 is formed above the end part, and an emitter bonding pad 33 of a large area is formed. The part between the pad 33 and the region 22 is electrically insulated by an oxide film 28. A low specific resistance value region 34 in which the impurity of the same type as that of the region 23 is diffused in high concentration near the surface is formed under the oxide film, and the conductivity necessary for functioning as a base is assured.