Embodiments for forming improved bipolar transistors are provided, manufacturable by a CMOS IC process. The improved transistor comprises an emitter having first and second portions of different depths, a base underlying the emitter having a central portion of a first base width underlying the first portion of the emitter, a peripheral portion having a second base width larger than the first base width partly underlying the second portion of the emitter, and a transition zone of a third base width and lateral extent lying laterally between the first and second portions of the base, and a collector underlying the base. The gain of the transistor is larger than a conventional bipolar transistor made using the same CMOS process. By adjusting the lateral extent of the transition zone, the properties of the improved transistor can be tailored to suit different applications without modifying the underlying CMOS IC process.