Polysilicon quantization effects on the electrical properties of MOS transistors

The quantum-mechanical behavior of charge carriers at the polysilicon/oxide interface is investigated. It is shown that a dark space depleted of free carriers is created at the interface as a consequence of the abrupt potenti al energy barrier, which dominates the polysilicon capacitance and voltage drop in all regions of operation of modern MOS devices. Quantum-mechanical effects in polysilicon lead to a reduction in the gate capacitance in the s ame way as substrate quantization, and to a negative voltage shift, which i s opposed to the positive shift caused by carrier quantization in the chann el. Effects on the extraction of device physical parameters such as oxide t hickness and polysilicon doping are also addressed.