A novel dual gate oxide （DGO） process is proposed to improve the performance of high voltage CMOS （HVCMOS） devices and the compatibility between thick gate oxide devices and thin gate oxide devices. An extra sidewall is added in this DGO process to round off the step formed after etching the thick gate oxide and poly-silicon. The breakdown voltages of high voltage nMOS （HVnMOS） and high voltage pMOS （HVpMOS） are 168 and - 158V, respectively. Excellent performances are realized for both HVnMOS and HVpMOS devices. Experimental results demonstrate that the HVCMOS devices work safely at an operation voltage of 100V.
The effects of total ionizing dose radiation on direct current （DC） and small-signal radio frequency （RF） performance of multi-finger RF partial deplete silicon-on-insulator lateral double diffused MOS （PDSOI LDMOS） transistors are investigated. The radiation response of the LDMOS transistors with different device structures is characterized for an equivalent gamma dose up to 1Mrad（Si） at room temperature. The front and back gate threshold voltages, off-state leak- age, transconductance, and output characteristics are measured before and after radiation, and the results show a significant degradation of DC performance. Moreover, high frequency measurements for the irradiated transistors indicate remarkable declines of S-parameters, cutoff frequency, and maximum oscillation frequency to 1Mrad（Si） exposure levels. Compared to the transistors with the BTS contact structure,the transistors with the LBBC contact do not show its excellent DC radiation hardness when the transistors operate at alternating current （AC） mode.
