Patent ID: 7719081

Claim:
A semiconductor device comprising: a semiconductor substrate of a first general conductivity type; an epitaxial layer of a second general conductivity type disposed on the semiconductor substrate; an isolation region of the first general conductivity type and isolating a portion of the epitaxial layer from another portion of the epitaxial layer; a buried diffusion layer of the second general conductivity type formed so as to extend in the semiconductor substrate and the epitaxial layer; a first diffusion layer of the second general conductivity type formed in the epitaxial layer so as to operate as part of a collector region; a diffusion layer of the first general conductivity type formed in the epitaxial layer so as to operate as a base region; a second diffusion layer of the second general conductivity type formed in the diffusion layer of the first general conductivity type so as to operate as an emitter region; and a third diffusion layer of the second general conductivity type formed in the epitaxial layer between the isolation region and the diffusion layer of the first general conductivity type, wherein the first diffusion layer of the second general conductivity type, the diffusion layer of the first general conductivity type, the second diffusion layer of the second general conductivity type and the third diffusion layer of the second general conductivity type are all disposed in a single portion of the epitaxial layer isolated by the isolation region, the single portion of the epitaxial layer isolated by the isolation region comprises no other isolation region so as not to be divided into two or more portions electrically isolated from each other, and the third diffusion layer of the second general conductivity type is not part of the collector region.