In dark conditions, an inversion layer of electrons will build up under the buried oxide
by thermal generation and enlarge the positive depletion layer in the n-type region, eventually closing the channel.
With such a thin-film, source and drain junction/depletion width of the MOS transistors can be easily bottomed to the buried oxide, thus reducing the junction capacitance.
As pointed out earlier, the buried oxide layer offers a complete isolation between the active device region and the bulk substrate.
One is oxidized at its surface to form what will become the buried oxide
A negative gate potential [V.sub.GS] is applied to the bottom side of the p-type silicon substrate such that a negatively charged depletion layer appears under the buried oxide layer.
If carriers are now generated by illumination they can accumulate below the buried oxide and form an inversion layer.
A special heating process recrystallizes the polysilicon, using the wafer itself as seed material to form a thin film of single-crystal silicon on the buried oxide
. The wafer is then sent to a semiconductor fab.