Subthreshold currents in CMOS transistors made on oxygen-implanted silicon

Kinks have been observed in subthreshold current plots of mesa-shaped n-channel transistors made on oxygen implanted silicon substrates. The kinks represent additional current flow and are due to overlapping fields from the gate electrode causing early corner inversion and to a Qss side-wall effect. Subthreshold currents in n-channel transistors are dominated by the two effects which, as a consequence, reduce threshold voltages especially in narrow n-channel transistors. The subthreshold characteristics of p-channel transistors were not affected in the same way.