Novel polysilicon sidewall gate silicon-on-sapphire MOSFET for power amplifier applications

We report the processing and DC and microwave characteristics of a novel thin-film silicon-on-sapphire MOS transistor which utilizes a sidewall process to realize a deep sub-micron gate length without the use of lithography. The device also incorporates an asymmetric lightly doped drain region for high breakdown voltage. Devices with 0.15 and 0.25 /spl mu/m gate lengths have been fabricated. A FET with a 0.25 /spl mu/m gate length and 1.0 /spl mu/m LDD length had an f/sub t/=9 GHz, f/sub max/=27 GHz and breakdown voltage of 13 volts.