Physics of the Subthreshold Slope - Initial Improvement and Final Degradation in Short CMOS Devices

The understanding of the behaviour of the threshold voltage Vth and the subthreshold slope S with technological parameters is of first importance. Indeed, the leakage current Ioff mainly depends on both. It is also quite clear that the Vth should be controlled through the optimisation of channel doping and/or through the use of shallow junctions. Nevertheless, although extensively studied [1][2][3][4] and intuitively accepted, the link between the degradation of S and the device architecture (channel length and junction depth) has never been analytically modelled.