A simple method for formation of the buffer layer in n-channel LDMOS

We propose a simple and cost-effective process of die buffer region which enhances the safe operation area (SOA) of the lateral double diffused MOSFETs (LDMOSFETs). Field oxide used for LOCOS isolation in conventional low voltage CMOS process is grown selectively around n+ drain of LDMOSFETs, which acts as buffer region around n+ drain with the help of dopant redistribution at silicon surface. The 150 V rating n-channel LDMOSFETs optimized using the proposed method have the best-reported specific on-resistance of 3.91 m/spl Omega/ cm/sup 2/ and higher second breakdown voltage by 20 V than that of conventional LDMOSFETs.