In this paper, for the first time, the transfer characteristic of a ‘U’-shaped gated tunnel FET (TFET) has been thoroughly investigated considering the real-time adverse effects of gate-to-drain direct tunneling current and gate-induced drain leakage (GIDL) effect using SILVACO ATLAS device simulator. Clearly, these leakage phenomena degrade the device performance, especially for low standby power (LSTP) operation. Hence, for the first time, a novel design modification has been proposed in terms of the optimization of the oxide thickness (TGD) of right vertical arm of the U-shaped gate, in order to mitigate the aforementioned problem. It has been found that when the TGD value is increased to 7 nm from the equivalent oxide thickness (EOT) value of 1.6 nm, the ultimate device becomes optimized in terms of the performance matrices like, IOFF, SSmin, ION/IOFF, etc. Moreover, 43% reduction in delay and almost 11 decades of OFF-state power reduction have been obtained for the optimized device than that of the device having TGD = 1.6 nm, for gate length of 70 nm. © 2021, The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.