Semiconductor device

A semiconductor device comprising:

• a first oxide;
• a second oxide over the first oxide;
• a source electrode;
• a drain electrode;
• a third oxide over the second oxide, the source electrode, and the drain electrode;
• a gate insulating film over the third oxide;
• and
• a gate electrode over the gate insulating film,
• wherein the third oxide is in contact with a top surface of the second oxide,
• wherein the source electrode is electrically connected to the second oxide,
• wherein the drain electrode is electrically connected to the second oxide,
• wherein each of the first oxide, the second oxide, and the third oxide includes In, an element M, and Zn,
• wherein the element M is Al, Ga, Y, or Sn,
• wherein an atomic ratio of the In, the Zn, and the element M in the second oxide is equal to or similar to an atomic ratio of the In, the Zn, and the element M in the third oxide, and
• wherein in each of the second oxide and the third oxide, an atomic proportion of the In is larger than an atomic proportion of the element M.