Semiconductor device

A semiconductor device comprising:

• an oxide semiconductor layer;
• a first electrode layer over and in contact with the oxide semiconductor layer;
• a second electrode layer over and in contact with the oxide semiconductor layer;
• a first insulating layer over the first electrode layer and the second electrode layer, the first insulating layer comprising an opening;
• a second insulating layer over the first insulating layer and the oxide semiconductor layer, the second insulating layer being in contact with a part of the oxide semiconductor layer;
• and
• a gate electrode layer over the second insulating layer, the gate electrode layer overlapping the part of the oxide semiconductor layer,
• wherein the opening of the first insulating layer and the part of the oxide semiconductor layer overlap each other.

A semiconductor device comprising:

• an oxide semiconductor layer;
• a first electrode layer over and in contact with the oxide semiconductor layer;
• a second electrode layer over and in contact with the oxide semiconductor layer;
• a first insulating layer over the first electrode layer and the second electrode layer, the first insulating layer comprising an opening;
• a second insulating layer over the first insulating layer and the oxide semiconductor layer, the second insulating layer being in contact with a part of the oxide semiconductor layer;
• and
• a gate electrode layer over the second insulating layer, the gate electrode layer overlapping the part of the oxide semiconductor layer,
• wherein a side surface of the second insulating layer is aligned with a side surface of the gate electrode layer, and
• wherein the opening of the first insulating layer and the part of the oxide semiconductor layer overlap each other.

A semiconductor device comprising:

• an oxide semiconductor layer;
• a first electrode layer over and in contact with the oxide semiconductor layer;
• a second electrode layer over and in contact with the oxide semiconductor layer;
• a first insulating layer over the first electrode layer and the second electrode layer, the first insulating layer comprising an opening;
• a second insulating layer over the first insulating layer and the oxide semiconductor layer, the second insulating layer being in contact with a part of the oxide semiconductor layer;
• and
• a gate electrode layer over the second insulating layer, the gate electrode layer overlapping the part of the oxide semiconductor layer,
• wherein a thickness of the second insulating layer is smaller than a thickness of the first insulating layer, and
• wherein the opening of the first insulating layer and the part of the oxide semiconductor layer overlap each other.