Patent ID: 6198156
Filing Date: 2001-03-06
Classification: H01L

Abstract:
Vertical bipolar power transistor, principally intended for radio frequency applications, especially for use in an amplifier stage in a radio base station, comprising:a substrate of a first conductivity type;a collector layer of the first conductivity type provided on the substrate;a first region of a second conductivity type adjacent to an upper surface of the collector layer; anda second region of said first conductivity type adjacent to the first region,wherein a degree of doping N.sub.c (x) of the collector layer varies from said upper surface and downwards to at least half a depth of the collector layer according to a polynom of at least a second degree of,N.sub.c =a.sub.0 +a.sub.1 x+a.sub.2 x.sup.2,where a.sub.0 is the degree of doping at the upper surface, x is a vertical distance from the upper surface, and a.sub.1, a.sub.2, are predetermined constants.