Semiconductor device and method for manufacturing semiconductor device

A semiconductor device comprising a transistor,

• wherein the transistor comprises a first insulator;
• a first oxide over the first insulator;
• a second oxide over the first oxide;
• a third oxide over the second oxide;
• a first conductor and a second conductor over the second oxide;
• a second insulator over the third oxide;
• a third conductor over the second insulator;
• a fourth insulator over the first conductor and the second conductor;
• and a third insulator over the fourth insulator,
• wherein an opening reaching the second oxide is provided in the third insulator and the fourth insulator,
• wherein the third oxide is positioned to cover an inner wall of the opening,
• wherein the second insulator is positioned to cover the inner wall of the opening with the third oxide therebetween,
• wherein the third conductor is positioned to fill the opening with the third oxide and the second insulator therebetween,
• wherein on the basis of a bottom surface of the first insulator, a level of a bottom surface of the third conductor in a region not overlapping with the second oxide is lower than a level of a bottom surface of the second oxide in a channel width direction of the transistor, and
• wherein a length of the bottom surface of the third conductor in the region not overlapping with the second oxide is shorter than a length of the bottom surface of the third conductor in a region overlapping with the second oxide in a channel length direction of the transistor.

A semiconductor device comprising a transistor,

• wherein the transistor comprises a first insulator;
• a first oxide over the first insulator;
• a second oxide over the first oxide;
• a third oxide over the second oxide;
• a first conductor and a second conductor over the second oxide;
• a second insulator over the third oxide;
• a third conductor over the second insulator;
• a fourth insulator over the first conductor and the second conductor;
• and a third insulator over the fourth insulator,
• wherein an opening reaching the second oxide is provided in the third insulator and the fourth insulator,
• wherein the third oxide is positioned to cover an inner wall of the opening,
• wherein the second insulator is positioned to cover the inner wall of the opening with the third oxide therebetween,
• wherein the third conductor is positioned to fill the opening with the third oxide and the second insulator therebetween, and
• wherein a side end portion of the fourth insulator has a curved shape when the transistor is seen from the above.