Short for silicon-on-insulator, a type of semiconductor fabrication technique developed by IBM. Unlike CMOS-based chips that are doped with impurities that enable a chip to store capacitance that must be discharged and recharged, SOI chips are formed by setting transistors on a thin silicon layer that is separated from the silicon substrate by an insulating layer of thin silicon oxide or glass, which minimizes capacitance (or the energy absorbed from the transistor).
SOI Explained This 2000 article from SysOpt.com explains SOI technology with useful diagrams.
