Editing Silicon on sapphire (section)

== 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&nbsp;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&nbsp;nm.{{Citation needed|date=March 2021}}