Semiconductor device, memory device, and method for manufacturing semiconductor device

A semiconductor device comprising:

• a first semiconductor layer having a cylindrical shape;
• a first conductive layer in contact with a bottom surface of the first semiconductor layer;
• a second conductive layer in contact with a top surface of the first semiconductor layer;
• a second semiconductor layer covering a side surface of the first semiconductor layer;
• a first insulating layer covering at least a part of a side surface of the second semiconductor layer;
• and
• a third conductive layer facing the side surface of the first semiconductor layer with the first insulating layer therebetween,
• wherein the first insulating layer comprises a first region between the first semiconductor layer and the third conductive layer and a second region between the first conductive layer and the third conductive layer, and
• wherein a width of the first region in a direction from the first semiconductor layer toward the third conductive layer is equal to or substantially equal to a width of the second region in a direction from the first conductive layer toward the third conductive layer.

A method for manufacturing a semiconductor device comprising:

• forming a first conductive layer;
• forming a semiconductor layer having a cylindrical shape over the first conductive layer;
• forming a first insulating layer over the first conductive layer and the semiconductor layer;
• processing the first insulating layer so that a part of a side surface of the semiconductor layer is exposed;
• forming a second insulating layer and a conductive film in this order over the first insulating layer and the semiconductor layer;
• processing the conductive film to form a second conductive layer whose top surface is positioned closer to the first conductive layer than a top surface of the semiconductor layer is;
• and
• forming a third conductive layer over the semiconductor layer and the second insulating layer.