A novel planar vertical double-diffused metal-oxide- semiconductor field-effect transistor with inhomogeneous floating islands

A novel planar vertical double-diffused metal-oxide-semiconductor (VDMOS) structure with an ultra-low specific on-resistance (R_on,sp), whose distinctive feature is the use of inhomogeneous floating p-islands in the n-drift region, is proposed. The theoretical limit of its R_on,sp is deduced, the influence of structure parameters on the breakdown voltage (BV) and R_on,sp are investigated, and the optimized results with BV of 83 V and R_on,sp of 54 mOmega cdotmm² are obtained. Simulations show that the inhomogeneous-floating-islands metal-oxide-semiconductor field-effect transistor (MOSFET) has a superior “R_on,sp/BV” trade-off to the conventional VDMOS (a 38% reduction of R_on,sp with the same BV) and the homogeneous-floating-islands MOSFET (a 10% reduction of R_on,sp with the same BV). The inhomogeneous-floating-islands MOSFET also has a much better body-diode characteristic than the superjunction MOSFET. Its reverse recovery peak current, reverse recovery time and reverse recovery charge are about 50, 80 and 40% of those of the superjunction MOSFET, respectively.