A vertical GaN reverse trench-gate power MOSFET (RT-MOSFET) device is proposed. This Vertical RT-MOSFET features the negative incline of broaden-trench sidewalls at the bottom of the gate. Numerical device simulations using TCAD have been carried out for device and circuit performance study and analysis. The device performance like transfer characteristics, on-state, off-state characteristics, capacitance–voltage characteristics is observed. The simulation results are shown in comparison to the conventional such as perpendicular trench-gate (UT), and trapezoidal trench-gate (VT)-MOSFET devices. The RT-MOSFET has a ~ 9% and ~ 20% reduced on-state resistance (Ron), ~ 6% and ~ 10% enhanced electrical breakdown voltage (Vbr), and ~ 21% and ~ 46% superior Baliga's figure of merits (Vbr2/Ron)compared to UT-MOSFET and VT-MOSFET, respectively. Next, we obtain lower energy loss using TCAD Mixed-mode simulation for DC-DC boost converter circuit performance with different voltage. The RT-MOSFET saves ~ 30% and ~ 76% energy loss at 100 V, ~ 43%, and ~ 75% energy loss at 200 V and ~ 54% and ~ 87% energy loss at 400 V during DC-DC converter application compared to UT-MOSFET and VT-MOSFET, respectively. © 2020, The Korean Institute of Electrical and Electronic Material Engineers.