Dielectric RESURF as an alternative to shield RESURF for an improved and easy-to-manufacture low voltage trench MOSFETs

Abstract

Shielded-gate trench or “Shield RESURF (REduced SURface Field)” MOSFETs have been well known for its lower RDS(ON) ×Area, and lower Rds(on)×Qgd figure of merits (FoMs), and used widely in the low to medium voltage applications (25 V to 200 V). However, this improvement is achieved at the expense of higher output capacitance or output charge (Coss or Qoss), which has become an increasingly important factor contributing to the MOSFET's switching power loss. In this paper, we will investigate the conventional single gate trench MOSFET structure based on the “dielectric RESURF” principle to offer a simpler wafer processing and consequently cheaper die cost, along with reduced switching losses at the output capacitance (Qoss), without compromising much the other key figure of merits such as Rds(on)×Area, and Rds(on)×Qg.