A Novel Buried Partial P+ Layer SOI High Voltage Device Structure with a Back Gate (BPP+SOI) is proposed. At the source side

the vertical electric field of the buried layer is increased and the surface electric field of PN junction is reduced due to the Partial P+ layer on the buried oxide of this structure; therefore

the breakdown voltage of the structure is greatly increased when the back gate bias is increased. Moreover

the specific on-resistance is reduced significantly. The simulation results show that the breakdown voltage of the BPP+SOI increases by 84.9 % at the 650V back gate bias and 150m drift region length while the specific on-resistance decreases by 31% at the same breakdown voltage and 120m drift region length.