Indium-zinc-oxide thin-film transistors (IZO-TFTs) are prepared with the multilayer structure of molybdenum-aluminum-molybdenum (Mo/Al/Mo) as the source/drain (S/D) electrode. Experiment demonstrates that the sputtering power of Mo (bottom layer of Mo/Al/Mo S/D) influences the performance of TFTs significantly. As the sputtering power increases, the Von runs negative shift, and the device uniformity degrades. XPS depth profile shows that the diffusion at the interface (IZO/Mo) occurs seriously. By decreasing the sputtering power, the diffusion can be suppressed and the devices are shown in normal off state (Von ～ 0.5 V, enhanced mode), with higher mobility (～ 13 cm2·V-1·s-1) and improved uniformity.