A Unified Quasi-3D Subthreshold Behavior Model for Multiple-Gate mosfets

Based on the quasi-3D potential approach, a unified subthreshold-potential, threshold-voltage, and subthreshold-current model is developed for multiple-gate mosfets including a quadruple-gate, triple-gate, and omega-gate mosfet. This work indicates that the scaling-length-oriented subthreshold current roll-up ΔI_sub and threshold voltage roll-off ΔV_th provide the physical insight into well-controlled short-channel effects (SCEs) in terms of effective scaling length λ_eff according to the scaling factor. Besides the decreased minimum conducting channel potential Φ_C,min, the smaller scaling-length-induced effective channel width/height (W_eff/H_eff) reflects the smaller effective conducting cross-sectional area, which reduces the subthreshold current degradation due to the increased subthreshold resistance R_sub. By accounting for the coupling factor in the quasi-3D potential approach, W_eff, H_eff, and Φ_C,min will be increased to some extent to decrease R_sub, which, hence, degrades the subthreshold behavior more extensively in response to SCEs.