Abstract: The lateral super junction (SJ) power devices suffer the substrate-assisted depletion (SAD) effect, which breaks the charge balance of SJ resulting in the low breakdown voltage (BV). A solution based on enhancing the electric field of the dielectric buried layer is investigated for improving the BV of super junction LDMOSFET (SJ-LDMOS). High density interface charges enhance the electric field in the buried oxide (BOX) layer to increase the block voltage of BOX, which suppresses the SAD effect to achieve the charge balance of SJ. In order to obtain the linear enhancement of electric field, SOI SJ-LDMOS with trenched BOX is presented. Because the trenched BOX self-adaptively collects holes according to the variable electric field strength, the approximate linear charge distribution is formed on the surface of the BOX to enhance the electric field according to the need. As a result, the charge balance between N and P pillars of SJ is achieved, which improves the BV of SJ-LDMOS to close that of the idea SJ structure.

Key words: super junction, LDMOS, substrate-assisted depletion effect