A 4H-SiC trench MOSFET with thick bottom oxide for improving characteristics

A 4H-SiC trench MOSFET has been developed that features the use of trench gates with a thick oxide layer on the bottoms of the trenches for relieving the electric field strength of the gate oxide layer. The maximum electric field strength and gate-drain charge (Qgd) of this device is 46% and 38% lower than that of a conventional MOSFET, respectively. A □5mm chip was fabricated with a thick oxide layer under the trench. The drain-source breakdown voltage (BVdss) of this chip is 1400V and the specific on-resistance (Ron.sp) is 4.4mΩcm² (Vg=20V, Vd=2V). A high breakdown voltage is obtained by a wide trench terminal structure and trench separation.