We investigated the impact of fin length (T-fin) on the threshold voltage (V-th) modulation by back bias (V-b) for independent double-gate (IDG) tunnel fin field-effect transistors (tFinFETs). It was found that V-th can be tuned by V-b for IDG tFinFETs regardless of T-fin, which can be explained by the back-gate-effect model of IDG FinFETs. For IDG tFinFETs, the slope (back-gate-effect factor (gamma)) of V-th with respect to V-b increases with thinning T-fin. This means that T-fin thinning is effective for tuning V-th by V-b for IDG tFinFETs. Furthermore, it was demonstrated that this back-bias-effect is consistent with the results of device simulation using an advanced nonlocal band-to-band model. (C) 2015 Elsevier Ltd. All rights reserved.