A method for compensating the threshold voltage roll-off using transistors
containing back-gates or body nodes is provided. The method includes
designing a semiconductor system or chip having a plurality of
transistors with a channel length of L.sub.nom. For the present
invention, it is assumed that the channel length of these transistors at
the completion of chip manufacturing is L.sub.max. This enables one to
set the off-current to the maximum value of I-off.sub.max which is done
by setting the threshold voltage value to Vt.sub.min. The Vt.sub.min for
these transistors is obtained during processing by using the proper
implant dose. After manufacturing, the transistors are then tested to
determine the off-current thereof. Some transistors within the system or
chip will have an off-current value that meets a current specification.
For those transistor devices, no further compensation is required. For
other transistors within the system or chip, the off-current is not
within the predetermined specification. For those transistors, threshold
voltage roll-off has occurred since they are transistors that have a
channel length that is less than nominal. For such short channel
transistors, the threshold voltage is low, even lower than Vt.sub.min,
and the off-current is high, even higher than I-off.sub.max. Compensation
of the short channel transistors is achieved in the present invention by
biasing the back-gate or body node to give increased threshold voltage
about equal to Vt.sub.min and hence an off-current that meets the
predetermined specification, which is about equal to I-off.sub.max.