A Novel SOI LDMOS with Folded Charge Trench

A novel silicon-on-insulator lateral double diffused metal oxide semiconductor with folded charge trench (FCT-SOI LDMOS) is proposed in this paper. The FCT-SOI is formed by introducing a row of folded charge trench on the buried oxide layer (BOX). The FCT-SOI structure can prevent the inversion layer charges of SOI from being expanded and extracted by the source depletion region, and the inversion layer charges fixed at the BOX interface can not only shield the power lines from the drain substrate to relieve the electric field peak at the drain, but also the electric field enhancement inside the BOX is guided by the interfacial Gauss’s theorem. In addition, the FCT-SOI structure additionally introduces a dielectric electric field in the drift region, realizing dual enhanced dielectric field (ENDIF) in SOI devices. FCT is suitable for high-voltage thick-film SOI devices, the folded charge trench is introduced at the bottom of the drift region, the current transport of the device is hardly affected, the breakdown voltage (BV) can be greatly increased without affecting the drift region resistance of the device. In this paper, the advantages of the breakdown voltage and current after the introduction of the FCT-SOI structure are analyzed and compared in same SOI film thickness devices.