Semiconductor device

A semiconductor device comprising:

• a first insulating layer;
• a second semiconductor layer comprising indium and oxygen, the second semiconductor layer being over the first insulating layer;
• a first semiconductor layer over the second semiconductor layer;
• a second insulating layer having a stacked-layer structure in which a first insulating film, a second insulating film, and a third insulating film are stacked in this order, the second insulating layer being over the first semiconductor layer;
• and
• a first conductive layer over the second insulating layer,
• wherein the first conductive layer is a gate electrode of a transistor,
• wherein the first semiconductor layer does not comprise gallium,
• wherein the first insulating film, the second insulating film, and the third insulating film each comprise an oxide, and
• wherein the first insulating film comprises a portion in contact with the first semiconductor layer.

A semiconductor device comprising:

• a first insulating layer;
• a second semiconductor layer over the first insulating layer;
• a first semiconductor layer over the second semiconductor layer;
• a second insulating layer having a stacked-layer structure in which a first insulating film, a second insulating film, and a third insulating film are stacked in this order, the second insulating layer being over the first semiconductor layer;
• and
• a first conductive layer over the second insulating layer,
• wherein the first insulating film, the second insulating film, and the third insulating film each comprise an oxide,
• wherein the first insulating film comprises a portion in contact with the first semiconductor layer,
• wherein the first semiconductor layer comprises indium and oxygen,
• wherein the second semiconductor layer comprises indium, zinc, gallium, and oxygen, and
• wherein the first semiconductor layer comprises a region having a higher indium content percentage than the second semiconductor layer.

A semiconductor device comprising:

• a first insulating layer;
• a second semiconductor layer over the first insulating layer;
• a first semiconductor layer over the second semiconductor layer;
• a second insulating layer over the first semiconductor layer;
• a metal oxide layer over the second insulating layer;
• and
• a first conductive layer over the metal oxide layer,
• wherein the first insulating layer comprises a portion in contact with the second semiconductor layer,
• wherein the first semiconductor layer comprises indium and oxygen,
• wherein the second semiconductor layer comprises indium, zinc, gallium, and oxygen,
• wherein the first semiconductor layer comprises a region having a higher indium content percentage than the second semiconductor layer,
• wherein the metal oxide layer comprises indium, and
• wherein the metal oxide layer and the first semiconductor layer have substantially the same indium content percentage.