A silicon integrated circuit technology using MOSFETs that are made on an insulating layer. The insulator provides good isolation between the transistors for improved performance at high speeds and high frequencies, as parasitic coupling and hence crosstalk between devices is reduced. The insulating layer can be provided by a nonconducting substrate upon which the silicon can be deposited, for example silicon-on-sapphire. Alternative techniques involve placing an insulating layer beneath the active layer during the manufacture of the integrated circuit. A silicon dioxide layer can be created deep in the silicon by ion implantation of oxygen; subsequent heat treatment produces a well-defined oxide layer.