A novel buffer super-junction(SJ) lateral double-diffused MOSFET(LDMOS) with an N-type buried layer(NB) is proposed. An N buffer layer is implemented under the SJ region and an N-type layer is buried in the P substrate. Firstly, the new electric field peak introduced by the p–n junction of the P substrate and the N-type buried layer modulates the surface electric field distribution. Secondly, the N buffer layer suppresses the substrate assisted depletion effect. Both of them improve the breakdown voltage(BV). Finally, because of the shallow depth of the SJ region, the NB buffer SJ-LDMOS is compatible with Bi-CMOS technology. Simulation results indicate that the average value of the surface lateral electric field strength of the NB buffer SJ-LDMOS reaches 23 V/ m at 15 m drift length which results in a BV of 350 V and a specific on-resistance of 21 m cm2. A novel buffer super-junction (SJ) lateral double-diffused MOSFET (LDMOS) with an N-type buried layer (NB) is proposed. An N buffer layer is implemented under the SJ region and an N-type layer is buried in the P substrate. Firstly, the new electric field peak introduced by the p-n junction of the P substrate and the N-type buried layer modulates the surface electric field distribution. These improve the breakdown voltage (BV). Finally, because of the shallow depth of the SJ region, the NB buffer SJ-LDMOS is compatible with Bi-CMOS technology. Simulation results indicate that the average value of the surface lateral electric field strength of the NB buffer SJ-LDMOS reaches 23 V / m at 15 m drift length which results in a BV of 350 V and a specific on-resistance of 21 m cm2.