Ultralow Specific on-Resistance Trench MOSFET with a U-Shaped Extended Gate

An ultralow specific on-resistance (R_on,sp) trench metal-oxide-semiconductor field effect transistor (MOSFET) with an improved off-state breakdown voltage (BV) is proposed. It features a U-shaped gate around the drift region and an oxide trench inserted in the drift region (UG MOSFET). In the on-state, the U-shaped gate induces a high density electron accumulation layer along its sidewall, which provides a low-resistance current path from the source to the drain, realizing an ultralow R_on,sp. The value of R_on,sp is almost independent of the drift doping concentration, and thus the UG MOSFET breaks through the contradiction relationship between R_on,sp and the off-state BV. Moreover, the oxide trench folds the drift region, enabling the UG MOSFET to support a high BV with a shortened cell pitch. The UG MOSFET achieves an R_on,sp of 2 mΩ·cm² and an improved BV of 216 V, superior to the best existing state-of-the-art transistors at the same BV level.