| CPC H01L 29/7869 (2013.01) | 8 Claims |
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1. A semiconductor device comprising:
a first gate electrode over a substrate;
a first gate insulating film over the first gate electrode;
a first oxide semiconductor layer over the first gate insulating film;
a second oxide semiconductor layer over and in contact with the first oxide semiconductor layer;
a source electrode and a drain electrode over the first oxide semiconductor layer;
an interlayer insulating film over the source electrode and the drain electrode;
a second gate insulating film in an opening of the interlayer insulating film; and
a second gate electrode over the second gate insulating film and in the opening of the interlayer insulating film,
wherein each of the first oxide semiconductor layer and the second oxide semiconductor layer comprises In, Ga, and Zn,
wherein the first oxide semiconductor layer has crystallinity,
wherein the second oxide semiconductor layer has crystallinity and c-axis alignment,
wherein the second oxide semiconductor layer comprises a first region in contact with a surface of the first oxide semiconductor layer and a second region in contact with a surface of the one of the source electrode and the drain electrode, and
wherein a direction of a c-axis of the first region is different from a direction of a c-axis of the second region.
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