Research on Breakdown Mechanism of LDMOS with Step Shallow Trench Isolation in the Drift Region

A novel LDMOSFET with Step Shallow Trench Isolation(SSTI) in the drift region is proposed． With this design, the effective length of drift region is increased, and the surface electrical field becomes more uniformly distributed, resulting in a higher breakdown voltag e. The device trench depth, gate length and doping concentration are further optimized. In computer simulation, when compared with a Monolayer-STI LDMOS(MSTI-LDMOS) with the same area, the breakdown voltage of the new device is 36% higher, and has a 14% lower on-resistance.