Abnormal Threshold Voltage Dependence on Gate Length in Ultrathin-Film n-Channel Metal-Oxide-Semiconductor Field-Effect Transistors (nMOSFET's) Using Separation by Implanted Oxygen (SIMOX) Technology

Abstract
We describe abnormal dependences of threshold voltage (V TH) on gate length in 8-nm-thick silicon-on-insulator (SOI) n-channel metal-oxide-semiconductor field-effect transistor (nMOSFET) devices on separation by implanted oxygen (SIMOX) substrates. It is shown experimentally that as the gate length decreases, V TH increases at 30 K. It is assumed that the parasitic resistances of the source and drain regions induce an effective negative substrate bias, and this model is used to formulate the V TH equation. It is strongly indicated that the freeze-out effect of the parasitic resistance contributes to the clear appearance of the V TH roll-up behavior by means of the effective negative substrate bias at temperatures less than 100 K.