Oxide film transistor and manufacturing method thereof

The invention discloses an oxide film transistor and a manufacturing method thereof. The manufacturing method comprises sequentially forming a grid electrode, a grid electrode insulating layer and an oxide semiconductor film layer; sequentially forming a first metal layer and a second metal layer on the oxide semiconductor film layer, and forming a drain electrode and a source electrode on the second metal layer, wherein the source electrode and the drain electrode are separated through a channel which exposes a part of the first metal layer; oxidizing the exposed part of first metal layer; forming an insulating passivation layer and setting a contact electrode. The manufacturing method of the oxide film transistor can protect the back channel of the oxide film transistor and meanwhile simplify the manufacturing process and save the cost.