A novel high-voltage sustaining structure with buried oppositely doped regions

A novel high-voltage sustaining structure with buried oppositely doped regions is demonstrated. Due to the compensation of the electric field provided by these regions, the resistivity and/or the thickness of the voltage-sustaining layer can be made smaller than that of a conventional one with the same breakdown voltage, and therefore the on-resistance (of unipolar conduction) can be reduced, The theory developed for designing such structures is found to be in good agreement with the results obtained from two-dimensional (2-D) simulation as well as from experiment. A 500 V VD-MOST using such a structure as the drift region and with proper edge termination is fabricated. Results show that its on-resistance is loner than the value given by the conventional "silicon limit."