Semiconductor device, semiconductor storage device, and method for manufacturing the same

A semiconductor device comprising:

• an upper electrode;
• an oxide semiconductor that has an upper end connected to and in contact with the upper electrode and a lower end, and extends in an up-down direction;
• a gate insulating film provided on a side surface of the oxide semiconductor;
• a gate electrode facing the side surface of the oxide semiconductor via the gate insulating film;
• and
• a first layer that is provided below the gate electrode and connected to the gate insulating film, wherein
• the gate insulating film includes an extended insulating portion extending downwardly into the first layer.

A method for manufacturing a semiconductor device comprising:

• forming a hole portion that penetrates through a first insulating layer, a gate electrode provided below the first insulating layer, and a second insulating layer provided below the gate electrode to expose a first layer provided below the second insulating layer;
• forming a gate insulating film covering the hole portion;
• forming a protection film covering the gate insulating film;
• removing a part of the protection film covering the first layer;
• removing a part of the gate insulating film covering the first layer;
• removing the protection film;
• and
• forming a semiconductor inside the hole portion.

A method for manufacturing a semiconductor device, comprising:

• forming a hole portion that penetrates through a first insulating layer, a gate electrode provided below the first insulating layer, and a second insulating layer provided below the gate electrode to expose a first layer provided below the second insulating layer;
• forming a sacrificial film covering the hole portion;
• removing a part of the sacrificial film covering the first layer to expose an upper surface of the first layer;
• forming a monolayer on the exposed upper surface of the first layer, the monolayer not covering a surface of an inner surface of the hole portion;
• removing the sacrificial film;
• forming a gate insulating film on the surface of the inner surface of the hole portion;
• removing the monolayer;
• and
• forming a semiconductor inside the hole portion.

A method for manufacturing a semiconductor device, comprising:

• forming a hole portion that penetrates through a first insulating layer, a gate electrode provided below the first insulating layer, and a second insulating layer provided below the gate electrode to expose a first layer provided below the second insulating layer;
• forming a gate insulating film covering the hole portion;
• forming a sacrificial film covering the gate insulating film below the hole portion;
• forming a monolayer covering a part of the gate insulating film that is left uncovered by the sacrificial film in the hole portion;
• removing the sacrificial film to expose a part of the gate insulating film that has been covered by the sacrificial film;
• removing a part of the gate insulating film covering the first layer in the hole portion to expose the first layer;
• removing the monolayer;
• and
• forming a semiconductor inside the hole portion.