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A new buffered super junction (SJ) LDMOS on silicon-on-insulator (SOI) is proposed to eliminate the substrate-assisted depletion effect. The trenched buried oxide is self-adaptive to collect the additional charges according to the variable electric field strength, which forms a dynamic buffer between the SJ and the substrate. The collected charges compensate the N pillars, resulting in the charge balance between N and P pillars of the SJ. Numerical simulation results indicate that the proposed device features high breakdown voltage and low on-resistance. Introduction:The super junction (SJ) has been applied in power devices to further improve the trade-off between the breakdown voltage (BV) and the on-resistance (R on ) [1]. One of the main issues for the SJ concept applied in lateral devices is the charge interaction between the SJ region and underlying substrate in the off-state, which is called the substrate-assisted depletion (SAD) effect. This effect upsets the delicate charge balance between the N and P pillars of the SJ, resulting in the degradation of the BV. To eliminate the SAD effect, SJ/RESURF LDMOST [2], SJ-LDMOS on silicon-on-sapphire substrate [3], backetched [4], unbalanced SJ-LDMOSTs [5] etc, were reported. A SJ-LDMOS with N-buffer layer has been reported to reduce the SAD effect in bulk silicon [6]. An N-buffer layer between the pillars and the P-substrate is used to achieve charge compensation between the pillars, the N-buffer layer, and the P-substrate. The compensation charges coming from the N-buffer layer is uniform and fixed. A dynamic buffered SJ-LDMOS with trenched buried oxide (TBOX) is proposed to suppress the SAD effect in this Letter. The TBOX is selfadaptive to accumulate additional charges, which forms a dynamic buffer layer to achieve charge compensation. As a result, the proposed structure effectively eliminates the SAD effect in SOI SJ-LDMOS.

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