A Stepped Oxide Hetero-Material Gate Trench Power MOSFET for Improved Performance

Abstract

In this brief, we propose a new stepped oxide hetero-material trench power MOSFET with three sections in the trench gate (an N <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> poly gate sandwiched between two P <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> poly gates) and having different gate oxide thicknesses (increasing from source side to drain side). The different gate oxide thickness serves the purpose of simultaneously achieving the following: 1) a good gate control on the channel charge and 2) a lesser gate-to-drain capacitance. As a result, we obtain higher transconductance as well as reduced switching delays, making the proposed device suitable for both RF amplification and high-speed switching applications. In addition, the sandwiched gate with different work-function gate materials modifies the electric field profile in the channel, resulting in an improved breakdown voltage. By using 2-D simulations, we have shown that the proposed device structure exhibits about 32% enhancement in breakdown voltage, 25% reduction in switching delays, 20% enhancement in peak transconductance, and 10% reduction in figure of merit (product of ON-resistance and gate charge) as compared to the conventional trench-gate MOSFET.