Experimental results and simulation analysis of 250 V super trench power MOSFET (STM)

We propose a new structure of power MOSFET, i.e. Super Trench power MOSFET (STM). Instead of a conventional n-drift layer, STM has vertical P and N layers formed within mesa regions between adjacent trenches filled with insulator. The P and N stripe structure relaxes the electric field in off-state and makes possible a lower specific on-resistance (Ron, sp) than that of the conventional MOSFET. We fabricated a 250 V STM for the first time with only one additional mask over the conventional DMOS process, and the measured data show high breakdown voltage with highly doped n drift layer. The device simulation results show it should be possible to lower the Ron, sp to 5 mΩcm ² for a breakdown voltage of 300 V