Patent ID: 8779418

Claim:
A semiconductor device comprising: a gate electrode over an insulating surface; a gate insulating film over the gate electrode; an oxide semiconductor film over the gate insulating film, the oxide semiconductor film overlapping the gate electrode; a pair of metal oxide films over the oxide semiconductor film; and a source electrode and a drain electrode over the pair of metal oxide films, wherein the oxide semiconductor film comprises a first portion, a second portion and a third portion between the first portion and the second portion, wherein the source electrode overlaps the first portion of the oxide semiconductor film, wherein the drain electrode overlaps the second portion of the oxide semiconductor film, wherein each of the first portion and the second portion of the oxide semiconductor film comprises, on the pair of metal oxide films sides, a region where a concentration of one or a plurality of metals in the oxide semiconductor film is higher than a concentration of one or a plurality of metals in the third portion of the oxide semiconductor film, and wherein the pair of metal oxide films, the source electrode, and the drain electrode comprise a same metal material.