Semiconductor memory device and method of manufacturing semiconductor memory device

A semiconductor memory device comprising:

• a plurality of first conductor layers stacked in a first direction;
• a second conductor layer provided above the plurality of first conductor layers;
• a first semiconductor layer extending in the first direction through the plurality of first conductor layers;
• a second semiconductor layer including a first portion extending in the first direction through the second conductor layer and a second portion with a diameter in a cross section orthogonal to the first direction being larger than a diameter of the first portion, the second semiconductor layer in contact with the first semiconductor layer via the second portion;
• a first charge storage layer disposed between the plurality of first conductor layers and the first semiconductor layer;
• and
• a first insulator layer disposed between the first semiconductor layer and the second conductor layer, the first insulator in contact with the second portion of the second semiconductor layer.

A method of manufacturing a semiconductor memory device, the method comprising:

• forming a first stacked body including a plurality of first sacrificial materials stacked in a first direction;
• forming a first hole extending through the plurality of first sacrificial materials;
• sequentially forming a first insulator layer, a first semiconductor layer, and a first core in the first hole;
• removing at least a portion of the first core formed in the first hole to form a first space, the portion of the first core extending from an upper end of the first stacked body to a first depth;
• forming a second semiconductor layer in the first space;
• removing a portion of the first semiconductor layer and a portion of the second semiconductor layer formed in the first hole to form a second space, the portion of the first semiconductor layer and the portion of the second semiconductor layer extending from the upper end of the first stacked body to a second depth, the second depth being shallower than the first depth;
• and
• forming a second insulator layer in the second space.