Impact of Interface Roughness on Threshold-Voltage Variation in Ultrasmall Gate-All-Around and Double-Gate Field-Effect Transistors

Effects of interface roughness on the threshold-voltage variation of nanometer-size gate-all-around (GAA) and double-gate (DG) metal-oxide-semiconductor field-effect transistors (MOSFETs) are investigated using three-dimensional non-equilibrium Green's function formalism. It is found that DG MOSFETs have better robustness to the interface roughness compared to GAA MOSFETs. This is attributed to the fact that the GAA structure has additional quantum conferment along the gate-width direction of the DG structure. From numerical simulations, a simple analytical formula is derived, which describes the threshold-voltage variation in terms of the subband energy change and reduction in the transmission function. (C) 2010 The Japan Society of Applied Physics