In this work, we studied the effect of the different thickness buffer layer on the electrical characteristics of InZnO (IZO) transistors. We found that when a 20nm layer of indium‐aluminum‐zinc oxide (IAZO) was added as the buffer layer between S/D electrodes and the active layer, the IZO transistor exhibited optimum electrical performance, with a high on/off drain current ratio of 2.61 ×107, the field‐effect mobility (μFE) of 15.75 cm2/Vs, the subthreshold swing (SS) of 129.85 mV/decade, and the turn‐on voltage (VON) of ‐0.4 V.