Patent ID: 6750483
Filing Date: 2004-06-15
Classification: H01L

Abstract:
A silicon-germanium bipolar transistor, comprising:a silicon substrate; a first emitter region formed in said silicon substrate and having a first conduction type and an edge zone; a second base region formed in said silicon substrate, adjoining said emitter region and having a second conduction type opposite said first conduction type; a third collector region formed in said silicon substrate, adjoining said base region and having said first conduction type; a first space charge zone formed between said emitter region and said base region; a second space charge zone formed between said base region and said collector region; said base region and said edge zone of said adjoining emitter region being alloyed with germanium; said emitter region having a germanium concentration rising toward said base region; a junction region containing said first space charge zone and having a decreasing germanium concentration in the junction region and in a vicinity of the junction region, a profile of the germanium concentration decreasing such that the first space charge zone is located in a region with a negative graded germanium concentration profile; and said base region having a germanium concentration initially rising more sharply than in said junction region.