4H-SiC Trench MOSFET with Bottom Oxide Protection

Ensuring gate oxide reliability and low switching loss is required for a trench gate SiC-MOSFET. We developed a trench gate SiC-MOSFET with a p-type region, named Bottom P-Well (BPW), formed at the bottom of the trench gate for bottom oxide protection. We can see an effective reduction in the maximum bottom oxide electric field (Eox) and a significant improvement in dynamic characteristics with a grounded BPW, whose dV/dt is 76 % larger than that with a floating BPW due to reduction in gate-drain capacitance (Cgd). The grounded BPW is found to be an effective means of both suppressing Eoxand reducing switching loss.