In this report, a novel tunnel field-effect transistor (TFET) named ‘F-shaped TFET’ has been proposed and its electrical characteristics are analyzed and optimized by using a computer-aided design simulation. It features ultra-thin and a highly doped source surrounded by lightly doped regions. As a result, it is compared to an L-shaped TFET, which is a motivation of this work, the F-shaped TFET can lower turn-on voltage (V_ON) maintaining high on-state current (I_ON) and low subthreshold swing (SS) with the help of electric field crowding effects. The optimized F-shaped TFET shows 0.4 V lower V_ON than the L-shaped TFET with the same design parameter. In addition, it shows 4.8 times higher I_ON and 7 mV/dec smaller average SS with the same V_ON as that for L-shaped TFET.