A superjunction LDMOST with a floating oppositely doped buried layer in substrate

A superjunction LDMOST with a floating oppositely doped buried layer in p-substrate is proposed. The buried layer provides another pn junction to sustain drain voltage, reduces the substrate-assisted-depletion effect and generates new electric field, which modulates the bulk electric field in off-state. Simulation results show that the proposed structure achieves significant breakdown voltage improvement as well as low specific on-resistance. The average electric field nearly reaches to the critical electric field (1.5×10⁵ V/cm) when the reverse blocking voltage is about 1200 V.