Patent ID: 7342293

Claim:
A bipolar junction transistor (BJT) comprising: a collector region located in a semiconductor substrate surface and adjacent to a first shallow trench isolation (STI) region; an active base region located on the collector region and having an upper surface and a lower surface and comprising a single crystalline material; an extrinsic base region located on the active base region; an emitter region having at least a portion that extends through the extrinsic base region and contacts the upper surface of the active base region; and a second STI region that extends between the first STI region and the collector region and undercuts a portion of the active base region with an undercut angle of not more than about 90°, wherein said undercut angle is located between a first surface and a second surface of said second STI region, wherein said first surface abuts said lower surface of said active base region, wherein said second surface abuts said collector region, and wherein said first STI region laterally abuts said second STI region.