Thin film device

A thin film device, comprising a gate electrode on a substrate, a gate insulating film on the gate electrode, an oxide semiconductor film on the gate insulating film, and a source/drain electrode on the oxide semiconductor film, wherein

• a surface layer containing at least either fluorine or chlorine exists in a part of the oxide semiconductor film where the source/drain electrode is not superimposed, and
• a mixed layer containing a mixture of the composition element of the oxide semiconductor film and the composition element of the part of the source/drain electrode in contact with the oxide semiconductor film exists in an interface between the oxide semiconductor film and the source/drain electrode.

A thin film device, comprising a gate electrode on a substrate, a gate insulating film on the gate electrode, an oxide semiconductor film on the gate insulating film, and a source/drain electrode on the oxide semiconductor film, wherein

• a surface layer containing at least either fluorine or chlorine exists in a part of the oxide semiconductor film where the source/drain electrode is not superimposed,
• the thin film device further comprises a channel protection insulating film on the surface layer, and
• the surface layer also exists in a part of the oxide semiconductor film where the source/drain electrode is superimposed.

A thin film device, comprising a gate electrode on a substrate, a gate insulating film on the gate electrode, an oxide semiconductor film on the gate insulating film, and a source/drain electrode on the oxide semiconductor film, wherein:

• a mixed layer containing a mixture of a first composition element of the oxide semiconductor film and a second composition element of a part of the source/drain electrode in contact with the oxide semiconductor film exists in an interface between the oxide semiconductor film and the source/drain electrode;
• and
• a quantity of atoms of the first and second composition elements of the mixed layer changes from the source/drain electrode side towards the oxide semiconductor film side.