Patent ID: 6078095
Filing Date: 2000-06-20
Classification: H01L

Abstract:
A semiconductor power transistor device including a plurality of unit transistors, each of said unit transistors comprising:a semiconductor region of a first conductivity type having a main surface and serving as a collector;a diffusion layer of a second conductivity type formed in said semiconductor region of the first conductivity type to be in contact with said main surface and serving as a base;a diffusion layer of the first conductivity type formed in said diffusion layer of the second conductivity type to be in contact with said main surface and serving as an emitter; anda base contact portion formed on said main surface on said diffusion layer of the second conductivity type; whereinsaid diffusion layer of the second conductivity type has a convex portion, projecting in a first direction parallel with the main surface and towards said diffusion layer of the first conductivity type, at a portion where said base contact portion is formed;said diffusion layer of the first conductivity type having a convex portion projecting in said first direction at a portion corresponding to and spaced apart in said first direction from the convex portion of the diffusion layer of the second conductivity type;collectors, bases and emitters of respective unit transistors being electrically connected with each other in parallel via said semiconductor region and said diffusion layers;said diffusion layer of the second conductivity type also having a C-shaped or inverted C-shaped portion exposed to said main surface and being formed by an edge of the convex portion of said diffusion layer of the first conductivity type and a contiguous portion of said diffusion layer of the first conductivity type which circumscribes said C-shaped or inverted C-shaped portion, wherein a base resistance between respective base portions of said unit transistors is thereby increased, said base resistance having a value dependent upon physical dimensions of the convex portions of said diffusion layer of the first conductivity type and said diffusion layer of the second conductivity type, such that the power transistor device can safely operate over a wide range of power levels.