An improved isolation structure for use in an integrated circuit and a method
for making the same is disclosed. In a preferred embodiment, an silicon dioxide,
polysilicon, silicon dioxide stack is formed on a crystalline silicon substrate.
The active areas are etched to expose the substrate, and sidewall oxides are formed
on the resulting stacks to define the isolation structures, which in a preferred
embodiment constitute dielectric boxes containing the polysilicon in their centers.
Epitaxial silicon is grown on the exposed areas of substrate so that it is substantially
as thick as the isolation structure, and these grown areas define the active areas
of the substrate upon which electrical structures such as transistors can be formed.
While the dielectric box provides isolation, further isolation can be provided
by placing a contact to the polysilicon within the box and by providing a bias
voltage to the polysilicon.
