Vertical power-MOSFETs with local channel doping

In this work we present a new vertical approach for solving the tradeoff between breakdown capability and on state resistance for PowerMOS devices. We use a vertical transistor on an epitaxial layer. This concept allows the adjustment of the breakdown voltage due to the thickness of the epi-layer separately from the on-state resistance, which is defined by the vertical transistor. The transistor was fabricated by means of atomic layer deposition, which allows very small channel length and doping control on atomistic scale. Devices with breakdown voltages between 12 V and 40 V were fabricated. It is also shown that local channel doping (/spl delta/-doping) instead of homogenous doping in the switching transistor reduces the on state resistance of the device significantly.