Semiconductor device and method for manufacturing semiconductor device

A semiconductor device comprising:

• a first insulator;
• a first oxide over the first insulator;
• a second insulator provided between the first insulator and the first oxide;
• a second oxide in contact with the first insulator and in contact with a side surface of the first oxide;
• a first conductor and a second conductor provided over the first oxide and apart from each other;
• a third insulator over the first insulator, the second oxide, and the first oxide;
• and
• a gate electrode over the third insulator,
• wherein the gate electrode comprises a region overlapping with the first oxide,
• wherein the third insulator comprises a region in contact with a top surface of the first oxide, a side surface of the first conductor, and a side surface of the second conductor, and
• wherein the second insulator and the third insulator comprise a material which is less likely to pass oxygen than the second oxide.