This SOS technology has been licensed throughout the world. ESI Technology Ltd. in the UK have developed a wide range of pressure transducers and pressure transmitters that benefit from the outstanding features of silicon on sapphire. Peregrine Semiconductor has used SOS technology to develop RF integrated circuits (RFICs) including RF switches, digital step attenuators (DSAs), phase locked-loop (PLL) frequency synthesizers, prescalers, mixers/upconverters, and variable-gain amplifiers. These RFICs are designed for commercial RF applications such as mobile handsets and cellular infrastructure, broadband consumer and DTV, test and measurement, and industrial public safety, as well as rad-hard aerospace and defense markets. Hewlett-Packard used SOS in some of their CPU designs, particularly in the HP 3000 line of computers. Substrate analysis - SOS structure The application of epitaxial growth of silicon on sapphire substrates for fabricating MOS devices involves a silicon purification process that mitigates crystal defects which result from a mismatch between sapphire and silicon lattices. For example, Peregrine Semiconductor's SP4T switch is formed on an SOS substrate where the final thickness of silicon is approximately 95 nm. Silicon is recessed in regions outside the polysilicon gate stack by poly oxidation and further recessed by the sidewall spacer formation process to a thickness of approximately 78 nm. See also Silicon on insulator Radiation hardening References Further reading Thin film deposition Semiconductor device fabrication MOSFETs Silicon