Changes in effective channel length due to hot-electron trapping in short-channel m.o.s.t.s

Stressed operation of p-channel m.o.s.t.s in the pre-avalanche region can cause the injection of hot electrons into the gate oxide adjacent to the source and drain junction. Trapping of this injected charge causes a localised reduction of the threshold voltage near the stressed junction and a consequent reduction of the effective channel length. Measurement of the saturated output conductance shows that the Early effect is much reduced after selective charge trapping. The phenomenon can be explained by regarding the stressed transistors as a composite device consisting of a number of series-connected m.o.s.t.s with differing threshold voltages, and can be used deliberately to reduce short-channel effects in small m.o.s.t.s.