In this paper, we showed a novel Channel-On-Fin (COF) InGaZnO4 thin-film transistors (IGZO-TFTs) with ultra-scaled gate. The 23-nm practical gate length in the back-gate device was realized on P+ silicon substrate by the traditional spacer pattern shift technology. The devices obtained outstanding electrical characteristics, e.g., high on/off current ratio of 108, promising subthreshold swing (SS) of 98.3 mV/decade, and slight Drain-Induced Barrier Lowering (DIBL) of 11mV/V. In addition, the influence of gate insulator thickness was also investigated.