A novel RESURF LDMOS with embedded CB-layer

RESURF LDMOS resorts to lightly doping in the drift region to improve the breakdown voltage which inevitably increases the on-resistance. Here, a novel voltage-sustaining layer called the composite buffer layer (CB-layer for short) is proposed to be embedded in the RESURF LDMOS which significantly reduces the on-resistance, and the breakdown voltage is still high. The CB-layer consists of one n- and p-type layer, both of which are heavier doped to provide a good conductive channel for the carriers in the on-state. When the drift region is fully depleted in the off-state the whole residual charges in the CB-layer approximates to zero since they cancel each other out which means a high breakdown voltage is sustained.