Semiconductor device and manufacturing method of the semiconductor device

A method for manufacturing a semiconductor device, comprising the steps of:

• depositing a first insulator;
• depositing a first oxide film, a second oxide film, and a third oxide film in this order over the first insulator;
• performing first heat treatment;
• depositing a first conductive film, a first insulating film, and a second conductive film in this order over the third oxide film;
• processing the first oxide film, the second oxide film, the third oxide film, the first conductive film, the first insulating film, and the second conductive film into island shapes to form a first oxide, a second oxide, a first oxide layer, a first conductive layer, a first insulating layer, and a second conductive layer;
• removing the second conductive layer;
• depositing a fifth insulator over the first insulator, the first oxide, the second oxide, the first oxide layer, the first conductive layer, and the first insulating layer;
• depositing a sixth insulator over the fifth insulator;
• forming an opening reaching the second oxide in the first oxide layer, the first conductive layer, the first insulating layer, the fifth insulator, and the sixth insulator;
• forming, through the formation of the opening, a third oxide and a fourth oxide from the first oxide layer, a first conductor and a second conductor from the first conductive layer, and a seventh insulator and an eighth insulator from the first insulating layer;
• performing second heat treatment;
• depositing a fourth oxide film over the sixth insulator and in the opening;
• depositing a fifth oxide film over the fourth oxide film;
• removing, by a dry etching method, the fourth oxide film and the fifth oxide film deposited on side surfaces of the fifth insulator to the eighth insulator in the opening;
• removing the fourth oxide film and the fifth oxide film over the sixth insulator;
• forming a fifth oxide and a sixth oxide by leaving the fourth oxide film and the fifth oxide film on a bottom portion of the opening;
• depositing a second insulating film over the sixth oxide and the sixth insulator;
• depositing a third conductive film over the second insulating film;
• and
• forming a ninth insulator and a third conductor in the opening by polishing the third conductive film and the second insulating film by a CMP method until the sixth insulator is reached.