Silicon-on-lnsulator (SOI) technology has been around since the 1960s when so-called silicon on sapphire (SOS) was first introduced. Silicon on sapphire has been used for many years for the fabrication of spaceborne and high-speed integrated circuits. It is still used in the fabrication of radio-frequency circuits.

More recent SOI materials involve only silicon and silicon dioxide—the two most common materials used in the fabrication of integrated circuits—as opposed to SOS, which requires the use of an alumina substrate.

Silicon-on-insulator technology has been used for a long time in niche applications such as spacecraft electronics and devices operating in a hightemperature or radiative environment. Recently however much attention has been paid to SOI technology because it is extremely suitable for the fabrication of low-voltage integrated circuits. Such circuits are in high demand for all kinds of portable systems, ranging from cellular phones to laptop computers. In August of 1998, IBM, Sharp, and other semiconductor manufacturers announced the development of SOI chips for high-speed computing and telecommunication con-sumer electronics. Most major semiconductor companies are putting considerable effort into SOI-circuit development for mainstream low-power applications.