Semiconductor device

A semiconductor device comprising:

• a first insulating layer comprising aluminum oxide;
• an oxide semiconductor layer over the first insulating layer;
• a source electrode and a drain electrode electrically connected to the oxide semiconductor layer;
• a gate insulating layer over the source electrode and the drain electrode,
• a gate electrode over the gate insulating layer, the gate electrode overlapping with the oxide semiconductor layer;
• and
• a second insulating layer comprising aluminum oxide over the gate electrode,
• wherein the first insulating layer and the second insulating layer are in contact with each other in a region where the source electrode, the drain electrode, and the gate electrode are not provided.

A semiconductor device comprising:

• a first insulating layer comprising aluminum oxide;
• a first oxide layer over the first insulating layer;
• an oxide semiconductor layer over the first oxide layer;
• a second oxide layer over the oxide semiconductor layer;
• a source electrode and a drain electrode electrically connected to the oxide semiconductor layer;
• a gate insulating layer over the source electrode and the drain electrode,
• a gate electrode over the gate insulating layer, the gate electrode overlapping with the oxide semiconductor layer;
• and
• a second insulating layer comprising aluminum oxide over the gate electrode,
• wherein the first insulating layer and the second insulating layer are in contact with each other in a region where the source electrode, the drain electrode, and the gate electrode are not provided.