Silicon-on-insulator 'gate-all-around' MOS device

The total-dose radiation hardness of MOS devices is roughly inversely proportional to the square of the thickness of the oxide layers in contact with the silicon. In SOI (silicon-on-insulator) devices, the silicon layer sits on an oxide layer of typically 400 nm. It is proposed that a thin, gate-quality oxide can be realized at the front as well as the back of the devices, which should greatly enhance the radiation hardness. Double-gate devices (i.e. the same gate at the front and the back of the device) have been shown to have, at least theoretically, interesting short-channel and high transconductance properties. The only reported realization of such a device used a complicated, highly non-planar process (vertical devices) and left one edge of the device in contact with a thick oxide, which can be detrimental to rad-hard performances. Fabrication processes and device performances are described.<>