Random access memory device utilizing a vertically oriented select transistor
View Patent ↗A memory structure has a vertically oriented access transistor with an annular gate region. A transistor is fabricated such that the channel of the transistor extends outward with respect to the surface of the substrate. An annular gate is fabricated around the vertical channel such that it partially or completely surrounds the channel. A buried annular bitline may also be implemented. After the vertically oriented transistor is fabricated with the annular gate, a storage device may be fabricated over the transistor to provide a memory cell.
1. An integrated circuit device comprising:
an access device, the access device comprising:
a semiconductor pillar comprised of a semiconductor material having a doped region formed in the semiconductor pillar at an end of the semiconductor pillar, and
a semi-annular ring disposed about a portion of the semiconductor pillar, wherein the semi-annular ring comprises a conductive material; and
a memory cell being in contact with the doped region.
2. The integrated circuit device of claim 1 , wherein the semi-annular ring is disposed about approximately half of the semiconductor pillar.
3. The integrated circuit device of claim 1 , wherein the semi-annular ring is disposed about approximately one-third of the semiconductor pillar.
4. The integrated circuit device of claim 1 , wherein the semi-annular ring is disposed about approximately three-quarters of the semiconductor pillar.
5. The integrated circuit device of claim 1 , wherein the semiconductor pillar is cylindrical in shape.
6. The integrated circuit device of claim 1 , wherein the semiconductor pillar is geometric in shape.
7. The integrated circuit device of claim 1 , wherein the semiconductor pillar is circular in shape.
8. An integrated circuit device comprising:
an access device comprising:
a pillar of semiconductor material having a first doped region formed in the semiconductor pillar at a first end of the pillar and having a second doped region formed in the semiconductor material at a second end of the pillar,
a first semi-annular ring disposed about a portion of the pillar, the first semi-annular ring comprising a conductive material; and
a second semi-annular ring disposed about another portion of the pillar and directly adjacent to the second doped region, the second semi-annular ring being electrically isolated from the first semi-annular ring, wherein the second semi-annular ring comprises a conductive material; and
a memory cell in contact with the first doped region.
9. The integrated circuit device of claim 8 , wherein the pillar extends away from a surface of a substrate in a perpendicular direction.
10. The integrated circuit device of claim 8 , wherein the pillar extends away from a surface of a substrate in an approximately 45 degree direction.
11. The integrated circuit device of claim 8 , wherein the pillar extends away from a surface of a substrate in an angular direction between 45 degrees and 90 degrees.
12. An integrated circuit device comprising:
an access device comprising:
a pillar of semiconductor material having a doped region formed in the semiconductor pillar;
a first semi-annular ring disposed about approximately half of the pillar, the first semi-annular ring comprising a conductive material; and
a second semi-annular ring disposed about approximately another half of the pillar, the second semi-annular ring being electrically isolated from the first semi-annular ring, wherein the second semi-annular ring comprises a conductive material; and
a memory cell in contact with the doped region.
13. The integrated circuit device of claim 12 , wherein the second semi-annular ring is coupled to a bitline of a memory array.
14. The integrated circuit device of claim 12 , wherein the memory cell is formed at the end of the semiconductor pillar.
15. An integrated circuit device comprising:
an access device comprising:
a substrate having a surface;
a pillar of semiconductor material extending from the substrate surface and having a doped region formed in the semiconductor pillar;
a first semi-annular ring disposed about at least a portion of the pillar, the first semi-annular ring comprising a conductive material; and
a second semi-annular ring disposed about at least another portion of the pillar, wherein the second semi-annular ring being electrically isolated from the first semi-annular ring and being more proximate to the substrate surface than the first semi-annular ring, the second semi-annular ring comprising a conductive material; and
a memory cell in contact with the first doped region.
16. The integrated circuit device of claim 15 , wherein the pillar is configured to form a channel of a transistor and the first doped region is configured to form one of the drain and source of the transistor and the second doped region is configured to form the other of the drain and source of the transistor.
17. The integrated circuit device of claim 15 , wherein the first semi-annular ring is configured to form a gate of the transistor and further configured to induce conduction through the pillar between the first doped region and the second doped region when a voltage is applied to the first at least semi-annular ring.
18. The integrated circuit device of claim 15 , wherein the first semi-annular ring is coupled to a wordline of a memory array.
19. The integrated circuit device of claim 15 , further comprising a storage device coupled to the first doped region.
20. The integrated circuit device of claim 19 , wherein the storage device comprises a crown type storage capacitor.