An SOI trench LDMOST（TLDMOST）with ultra-low specific on-resistanceis proposed.It features double vertical high-k insulator pillars（Hk1 and Hk2）in the oxide trench,which are connected to the source electrode and drain electrode,respectively.Firstly,under reverse bias voltage,most electric displacement lines produced by the charges of the depleted drift region in the source side go through the Hk1,and thus the average electric field strength under the source can be enhanced.Secondly,two additional electric field peaks are induced by the Hk_1,which further modulate the electric field in the drift region under the source.Thirdly,most electric displacement lines produced by the charges of the depleted drift region in the drain side enter into the Hk2.This not only introduces one more electric field peak at the corner of the oxide trench around the Hk2,but also forms the enhanced vertical reduced surface field effect,which modulates the electric field in the drift region under the drain.With the effects of the two Hk insulator pillars,the breakdown voltage（BV）and the drift region doping concentration are significantly improved.The simulation results indicate that compared with the oxide trench LDMOST（previous TLDMOST）with the same geometry,the proposed double Hk TLDMOST enhances the BV by 86%and reduces theby 88%.
A lateral double-diffused metal-oxide-semiconductor field effect transistor （LDMOST） with multiple n-regions in the p-substrate is investigated in detail. Because of the decrescent n-regions, the electric field distribu- tion is higher and more uniform, and the breakdown voltage of the new structure is increased by 95%, in comparison with that of a conventional counterpart without substrate n-regions. Based on the trade-off between the breakdown voltage and the on-resistance, the optimal number of n-regions and the other key parameters are achieved. Furthermore, sensitivity research shows that the breakdown voltage is relatively sensitive to the drift region doping and the n-regions＇ lengths.
This paper presents an improved analytical model for an RF-LDMOST structure based on the 2D Poisson equation. The derived model indicates the influence of high doped shallow drift and low doping concentration p epitaxial layer on the electric field distribution. In particular, the importance of the thickness of the p epitaxial layer for electric field distributions in RF-LDMOST are shown through MATLAB analytical results based on the model. Then ISE TCAD simulations and experiments are processed and their results are in agreement with the analytical model. This model contributes to the comprehension and optimization design of RF-LDMOST.
A new super-junction lateral double diffused MOSFET （LDMOST） structure is designed with n-type charge compensation layer embedded in the p^--substrate near the drain to suppress substrate-assisted depletion effect that results from the compensating charges imbalance between the pillars in the n-type buried layer. A high electric field peak is introduced in the surface by the pn junction between the p^--substrate and n-type buried layer, which given rise to a more uniform surface electric field distribution by modulation effect. The effect of reduced bulk field （REBULF） is introduced to improve the vertical breakdown voltage by reducing the high bulk electric field around the drain, The new structure features high breakdown voltage, low on-resistance and charges balance in the drift region due to n-type buried layer.
