Hot carrier (HC) effect of top gate (TG) and dual gate (DG) with high mobility oxide thin film transistors (TFTs) is investigated. It is found that TFTs with TG structure have a severer current degradation behavior than DG structure TFTs after HC stress. Relative small local vertical and lateral electric field near the drain junction induced by the DG TFTs, associated with higher mobility of DG TFTs are both employed to understand the different HC effect behavior. The negative threshold voltage (Vth) shift with decreasing channel length due to the short channel effect is also discussed.