Effects of shallow trench isolation on silicon-on-insulator devices for mixed signal processing

The transconductance and the low-frequency noise of SOI MOSFETs with shallow trench isolation (STI) structures are investigated qualitatively for various device sizes and three different gate shapes. Devices with the channel region butted to the STI region show a reduction in the mobility and the increase in the low-frequency noise as the channel width is reduced. In comparison, the devices without STI butted channel region show a much lower reduction in the mobility and increase in the noise characteristics with the channel width. From the charge pumping and noise measurement results, the interface-state generated by the STI process is identified for the first time, as the cause of these anomalous phenomena.