Ultralow ON-Resistance High-Voltage p-Channel LDMOS With an Accumulation-Effect Extended Gate

The high ON-resistance and the limited breakdown voltage (BV) are the two major issues for the p-channel lateral double-diffused MOSFET (pLDMOS). To solve the two issues, an ultralow specific ON-resistance (RON,sp) pLDMOS with improved BV is proposed and investigated by simulation. It features an extended gate (EG) with accumulation effect over the drift region and a P + floating layer (PFL) in the N-sub. In the ON-state, the EG induces the hole accumulation layer along the drift region surface, providing an ultralow-resistance conducting path. This accumulation-type current transport mode makes RON,sp almost independent of the drift region doping concentration (N d ) and contributes to a much lower R ON,sp , which greatly breaks through the silicon limit of R ON,sp ∝ BV 2.5 . In the OFF-state, the EG not only modulates the surface electric field (E-field) distribution to enhance the BV, but also helps deplete the drift region to increase the optimized Nd, and thus further reduce R ON,sp . Moreover, the PFL is not depleted, and thus equipotential in the lateral direction. Therefore, the PFL not only modulates the bulk E-field distribution at the source and drain sides but also introduces an additional vertical diode to sustain a higher BV. Owing to the effects mentioned above, the simulated results show that the EG PFL pLDMOS decreases R ON,sp by 68% and increases the BV by 47% compared with the conventional pLDMOS.