Bidirectional, high-speed power mosfet devices with deep level

Abstract

Power MOSFET devices useful in synchronous rectifier circuit applications are bidirectional and symmetrical for use in AC circuits, and have low on-resistance, fast switching speed, and high voltage capability. In one embodiment, a planar enhancement-mode diffused MOSFET structure obviates the source-to-base short conventionally included to prevent turn-on of the parasitic bipolar transistor defined by the main terminal regions of one conductivity type and the intermediate base region of opposite conductivity type, by employing within the base region a recombination region having a relatively small lifetime for excess base region majority-carriers in order to inhibit operation of the parasitic bipolar transistor. Another embodiment resembles a pair of conventional, vertical-current, MOSFET unit cells formed symmetrically back-to-back and sharing a common drain region which serves only as an intermediate terminal region not directly connected to any device terminal. To inhibit operation of the several parasitic bipolar transistors and thyristor switching device structures inherent in this embodiment, an ohmic short is provided between the source and base regions of each of the unit cells, and a recombination region having a relatively small lifetime for intermediate terminal region majority-carriers is formed within the intermediate terminal region between the spaced base regions of the unit cells.