Bipolar transistor

Abstract

A bipolar transistor including an emitter region of a first conductivity type, having a predetermined width, an inner base region of a second conductivity type, formed below the emitter region and contacting the emitter region, thus forming a PN junction, an outer base region of the second conductivity type, having a high impurity concentration, set in ohmic contact with the edge of the inner base region and surrounding the inner base region, an inner collector region of the first conductivity type, formed below the inner base region and contacting the inner base region, thus forming a PN junction, and an outer collector region of the first conductivity type, set in ohmic contact with the inner collector region, contacting the lower surface of the outer base region, thus forming a PN junction, and surrounding the inner collector region. The transistor is characterized in the following respects. First, the inner collector region has a higher impurity concentration than the outer collector region. Second, the edge of the inner collector region is located right below, or inner than, the edge of the emitter region. Third, the upper surface of the inner collector region is higher and closer to the emitter region, than the upper surface of the outer collector region.

Dependencies are inferred from the claim text.