Investigation of a novel SOI LDMOS using p+ buried islands in the drift region by numerical simulations

Abstract

A novel SOI LDMOS with p+ buried islands and p-top layer in the drift region (PBI SOI) is proposed in this letter. At off-state, the high potential is induced from the drain region to the inside of the drift region. The p+ buried islands cause reduced surface field effect and modulate the electric field distribution in the drift region. The buried p-top layer withstands the lateral drain voltage. Thus, the breakdown voltage (BV) of PBI SOI is significantly improved. Meanwhile, the specific on-resistance $$(R_\mathrm{on,sp})$$ is reduced by improving doping concentration of the drift region, owing to the assisting depletion effect caused by the p+ buried islands. Consequently, the $$R_\mathrm{on,sp}$$ of the proposed structure is reduced by 53.7% compared with the conventional SOI LDMOS at the same half-pitch size, the BV and the figure-of-merit $$(\hbox {FOM} = \hbox {BV}^{2}/ R_\mathrm{on,sp})$$ are observably improved by 24.8% and 235.9% respectively.