Transistor, semiconductor memory device, and manufacturing method for transistor
A transistor includes an upper electrode; a lower electrode; a gate electrode disposed between the upper electrode and the lower electrode; and a columnar portion penetrating the gate electrode and provided between the upper electrode and the lower electrode. The columnar portion includes a tubular gate insulating film and a semiconductor layer, the tubular gate insulating film disposed at a first distance away from the upper electrode and in contact with the gate electrode. The semiconductor layer is embedded in the tubular gate insulating film and between the gate insulating film and the upper electrode and in contact with the upper electrode.
1. A transistor comprising:
an upper electrode;
a lower electrode;
a gate electrode disposed between the upper electrode and the lower electrode;
a columnar portion penetrating the gate electrode and disposed between the upper electrode and the lower electrode,
wherein the columnar portion includes a tubular gate insulating film and a semiconductor layer, the tubular gate insulating film disposed at a first distance away from the upper electrode and in contact with the gate electrode, the semiconductor layer embedded in the tubular gate insulating film and disposed between the tubular gate insulating film and the upper electrode and being in contact with the upper electrode; and
wherein at least a part of a side surface of a part of the semiconductor layer embedded between the tubular gate insulating film and the upper electrode is in contact with the upper electrode.
2. The transistor according to claim 1 , wherein the first distance is equal to or less than a film diameter of a part of the semiconductor layer embedded in the tubular gate insulating film.
3. The transistor according to claim 1 , wherein a film diameter of the part of the semiconductor layer embedded in the tubular gate insulating film, a film diameter of the part of the semiconductor layer embedded between the tubular gate insulating film and the upper electrode, and a radius of the columnar portion, have a relationship of T 2 a <T 2 b <T 3 where T 2 a is the film diameter of the part of the semiconductor layer embedded in the tubular gate insulating film, T 2 b is the film diameter of the part of the semiconductor layer embedded between the tubular gate insulating film and the upper electrode, and T 3 is the radius of the columnar portion.
4. The transistor according to claim 1 , wherein the semiconductor layer includes an oxide semiconductor.
5. The transistor according to claim 4 , wherein the semiconductor layer contains oxygen, indium, gallium, and zinc.
6. The transistor according to claim 4 , wherein the semiconductor layer contains at least one of indium, zinc, or tin.
7. The transistor according to claim 1 , wherein the semiconductor layer includes a recess portion in a middle on an upper electrode side, wherein at least a part of the recess portion of the semiconductor layer comes into contact with the upper electrode.
8. The transistor according to claim 1 , wherein the columnar portion is tapered.
9. A semiconductor memory device comprising the transistor according to claim 1 .
10. The semiconductor memory device according to claim 9 , wherein the transistor includes a transistor of a NAND flash memory.
11. The semiconductor memory device according to claim 9 , wherein the transistor is a transistor of a dynamic random access memory (DRAM).
12. The transistor according to claim 1 , wherein the semiconductor layer includes a channel.
13. The transistor according to claim 8 , wherein a radius of the columnar portion decreases toward the lower electrode.