In this study, channel potential for silicon-based doped dual-metal double-gate tunnel field-effect transistor structure is analytically solved using the evanescent-mode approach in the sub-threshold region. This method generally describes short channel effects in the entire channel region of the device structure and predicts different characteristic length λ which depends on tunnel current and does not depend along a transverse direction within the channel. The model is valid for the whole device structure rather than just semiconductor/insulator interfaces. The impact of variation of bias condition on channel potential is also investigated in the sub-threshold region. Finally, drain current is evaluated using Kane's and Kleysh's model and validated with a calibrated simulation, which has been carried out using 2D TCAD Sentaurus simulator.