Threshold Voltage of Ultrathin Gate-Insulator MOSFETs

This letter elucidates the difficulties in applying the conventional 2psi_B threshold voltage model for current MOSFETs with ultrathin gate insulator and presents a new comprehensive alternative for general MOSFETs. After high-k gate dielectric is successfully developed to acquire a strong gate control, the on-off switching of MOSFETs is no longer dependent on substrate doping concentration as before. A physical drift-current threshold voltage model is proposed directly from the drain current itself, where the threshold voltage is defined as the onset of the drift current playing the main contribution in the total drain current. It can properly predict threshold voltage for general MOSFET devices and appropriately provide a physical current criterion for extracting the threshold voltage.