Provided is a method of manufacturing a ZnO-based thin film transistor (TFT). The method may include forming source and drain electrodes using one or two wet etchings. A tin (Sn) oxide, a fluoride, or a chloride having relatively stable bonding energy against plasma may be included in a channel layer. Because the source and drain electrodes are formed by wet etching, damage to the channel layer and an oxygen vacancy may be prevented or reduced. Because the material having higher bonding energy is distributed in the channel layer, damage to the channel layer occurring when a passivation layer is formed may be prevented or reduced.