Patent ID: 8878173

Claim:
A semiconductor device comprising: a gate electrode; a gate insulating film covering the gate electrode and having a stacked structure including a first metal oxide film and a second metal oxide film; an oxide semiconductor film in contact with the second metal oxide film and in a region overlapping with the gate electrode; a source electrode and a drain electrode electrically connected to the oxide semiconductor film; a third metal oxide film over and in contact with the oxide semiconductor film; and a fourth metal oxide film over and in contact with the third metal oxide film, wherein the first metal oxide film, the second metal oxide film, the third metal oxide film, and the fourth metal oxide film each contain a Group 13 element and oxygen, wherein each of the source electrode and the drain electrode is surrounded by the second metal oxide film and the third metal oxide film in a cross-sectional view, such that the third metal oxide film contacts top and peripheral side surfaces of at least one of the source electrode and the drain electrode, and the second metal oxide film and the oxide semiconductor film contact a bottom surface of the at least one of the source electrode and the drain electrode.