Patent ID: 7560797
Filing Date: 2009-07-14
Classification: H01L

Abstract:
1. A semiconductor device comprising: a semiconductor substrate of a first general conductivity type; a first epitaxial layer of a second general conductivity type disposed on the semiconductor substrate; a second epitaxial layer of the second general conductivity type disposed on the first epitaxial layer; an isolation region of the first general conductivity type and isolating a portion of the first and second epitaxial layers from another portion of the first and second epitaxial layers; a buried diffusion layer of the second general conductivity type formed so as to extend in the semiconductor substrate and the first epitaxial layer; a first diffusion layer of the second general conductivity type formed in the second epitaxial layer so as to operate as a collector region; a first diffusion layer of the first general conductivity type formed in the second epitaxial layer so as to operate as a base region; a second diffusion layer of the second conductivity type formed in the first 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 second epitaxial layer between the isolation region and the first diffusion layer of the first general conductivity type, wherein an impurity concentration of the second epitaxial layer is higher than an impurity concentration of the first epitaxial layer, and an impurity concentration of the first diffusion layer of the second general conductivity type is higher than the impurity concentration of the second epitaxial layer, and the third diffusion layer of the second general conductivity type is connected electrically to the collector region.