A new method for forming a silicon-on-insulator MOSFET while eliminating floating
body effects is described. A silicon-on-insulator substrate is provided comprising
a silicon semiconductor substrate underlying an oxide layer underlying a silicon
layer. A first trench is etched partially through the silicon layer and not to
the underlying oxide layer. Second trenches are etched fully through the silicon
layer to the underlying oxide layer wherein the second trenches separate active
areas of the semiconductor substrate and wherein one of the first trenches lies
within each of the active areas. The first and second trenches are filled with
an insulating layer. Gate electrodes and associated source and drain regions are
formed in and on the silicon layer in each active area. An interlevel dielectric
layer is deposited overlying the gate electrodes. First contacts are opened through
the interlevel dielectric layer to the underlying source and drain regions. A second
contact opening is made through the interlevel dielectric layer in each of the
active regions wherein the second contact opening contacts both the first trench
and one of the second trenches. The first and second contact openings are filled
with a conducting layer to complete formation of a silicon-on-insulator device
in the fabrication of integrated circuits.