Transistor

Abstract

A transistor which has a plurality of ring emitter transistor units formed on a common semiconductor substrate having one conductivity type, each ring emitter transistor unit being provided with a base region of the opposite conductivity type from the semiconductor substrate and formed on its surface, an emitter region of the same conductivity type as the semiconductor substrate and formed in the base region to a depth smaller than the latter to have a ring-shaped plane configuration, a base electrode formed in the vicinity of the outer or inner periphery of the ring-shaped emitter region, an emitter electrode formed in the vicinity of the inner or outer periphery of the emitter region, and a ballasting resistor formed to interconnect the emitter region and the emitter electrode. The product of the area of the emitter region and the resistance value of the ballasting resistor is selected to be in the range of from 6.0 .times. 10.sup.-4 to 1.3 .times. 10.sup.-3 [.OMEGA..multidot.cm.sup.2 ], to provide for enhanced power handling capability of the transistor without a large reduction in its maximum current and to facilitate the design of this kind of transistor.