The context of silicon on insulator (SOI) technologies is reviewed in terms of wafer fabrication, configuration/ performance of SOI devices, and typical operation mechanisms in partially and fully depleted SOI MOSFETs. The future of SO[ is tentatively explored, by addressing the further scalability of SOI transistors as well as the innovating architectures (double-gate, ground-plane, and extremely thin MOSFETs) proposed for the ultimate generations of SOI transistors.