Provided are a transistor, a method of manufacturing the transistor, and an electronic device including the transistor. The transistor may include a gate insulator of which at least one surface is treated with plasma. The surface of the gate insulator may be an interface that contacts a channel layer. The interface may be treated with plasma by using a fluorine (F)-containing gas, and thus may include fluorine (F). The interface treated with plasma may suppress the characteristic variations of the transistor due to light.