Patent ID: 6521974
Filing Date: 2003-02-18
Classification: H01L

Abstract:
A bipolar transistor comprising:a silicon layer of a first conductivity type; a multi-layer film comprised of a first insulating film, a polycrystalline layer of a second conductivity type opposite to the first conductivity type and a second insulating film deposited, respectively, on the surface of the silicon layer of the first conductivity type; an opening in the multi-layer film; a first single crystal silicon germanium layer of a second conductivity type located in the opening; a second single crystal silicon germanium layer of the second conductivity type provided on the first single crystal silicon germanium layer of the second conductivity type; a polycrystalline silicon germanium layer of the second conductivity type provided so that it is in contact with the second single crystal silicon germanium layer of the second conductivity type and the polycrystalline layer of the second conductivity type; a first single crystal area of a first conductivity type provided on the second single crystal silicon germanium layer of the second conductivity type; and a second single crystal area of the first conductivity type formed to extend into a part of the first single crystal silicon germanium layer of the second conductivity type, further comprising: a single crystal layer which is provided on said second single crystal silicon germanium layer of the second conductivity type and in which the concentration of the impurities is lower than that in said second single crystal silicon germanium layer of the second conductivity type.