Abstract: A bipolar junction transistor (BJT) structure and fabrication method are provided in which a doped polysilicon filled trench is utilized to form both the extrinsic base contact region and a vertical field plate. A sacrificial mandrel of dielectric material is formed over regions that will become the BJT active area. This allows the polysilicon filled trench to be extended above the original semiconductor substrate surface. In this way, the base-collector and emitter-base junctions are both self-aligned to the field plate trench. The field plate is utilized to control and shape the electric field in the base-collector depletion region, allowing heavier collector well doping for the same breakdown voltage. This results in improvement in both the breakdown/Ron ratio and the fT*BVcbo product.

Abstract: The power delivered by an RF power transistor having cascaded cells or unit elements is improved by reducing the phase imbalance between elements and thereby reducing transverse effects between cells. Phase imbalance is reduced by varying the number of transistor elements connected to interconnect areas, connecting wire bonds to an input transmission line concentrated near an outer edge in the transmission line to take advantage of surface skin effects on current, and varying the surface area of the interconnect areas to adjust input impedance and output impedance of each cell.