Provided are a transistor, a method of manufacturing the transistor, and an electronic device including the transistor. The transistor may include a passivation layer on a channel layer, a source, a drain, and a gate, wherein the component of the passivation layer is varied in a height direction. The passivation layer may have a multi-layer structure including a silicon oxide layer, a silicon oxynitride layer, and a silicon nitride layer sequentially stacked. The channel layer may include an oxide semiconductor.