This letter investigates the degradation behavior under hot-carrier stress in InGaZnO thin film transistors with I- and U-shaped asymmetric electrodes. After hot-carrier stress, a serious Vt shift, as well as on-current and subthreshold swing degradations are observed in Id-Vg transfer curve under reverse mode. Moreover, it is found that the Vt instability is caused by hot-electron injection near the drain side, and this phenomenon which is verified by C-V measurement. Furthermore, the location of trapped hot-electron is estimated from the two-stage rise in the gate-to-drain/gate-to-source capacitance curves and then verified by the simulation tool. [ABSTRACT FROM AUTHOR]