Vertical memory device structures
View Patent ↗Vertically oriented semiconductor memory cells are added to a separately fabricated substrate that includes electrical devices and/or interconnect. The plurality of vertically oriented semiconductor memory cells are physically separated from each other, and are not disposed within the same semiconductor body. The plurality of vertically oriented semiconductor memory cells can be added to the separately fabricated substrate as a thin layer including several doped semiconductor regions which, subsequent to attachment, are etched to produce individual doped stack structures, which are then supplied with various dielectric coatings, gate electrodes, and contacts by means of further processing operations. Alternatively, the plurality of vertically oriented semiconductor memory cells may be completely fabricated prior to attachment. DRAMs, SRAMs, non-volatile memories, and combinations of memory types can be provided.
1. A semiconductor memory structure, comprising:
a substrate having electrical devices formed therein, and further having at least one dielectric layer and at least one interconnect layer disposed above the substrate; and
a first stackable add-on layer, the first stackable add-on layer including a plurality of vertically oriented semiconductor memory cells disposed within the first stackable add-on layer, the plurality of vertically oriented semiconductor memory cells separated from each other by dielectric material;
wherein the stackable add-on layer is bonded to a layer of the substrate that is the greatest distance from the substrate as measured from the bottom surface of the substrate; and
wherein the memory cell is a DRAM having at least one transistor.
2. The semiconductor memory structure of claim 1 , wherein the vertically oriented memory cell comprises a vertical transistor and a serially connected capacitor in a SOI pillar.
3. The semiconductor memory structure of claim 1 , wherein the vertically oriented semiconductor memory cell comprises a vertical transistor in an SOI pillar and a capacitor connected in series therewith, the capacitor disposed external to the first stackable add-on layer.
4. The semiconductor memory structure of claim 1 , wherein the vertically oriented semiconductor memory cell comprises:
a first capacitor,
a first access transistor serially connected to the first capacitor,
a second access transistor serial connected to the first access transistor, and
a second capacitor serially connected to the second access transistor;
wherein the first capacitor, the first access transistor, the second access transistor, and the second capacitor are all formed in a single vertically oriented SOI pillar.
5. The semiconductor memory structure of claim 1 , wherein the vertically oriented semiconductor memory cell comprises two vertically oriented, serially connected transistors formed on a SOI pillar, the serially connected transistors further connected to a capacitor disposed external to the stackable add-on layer.
6. The semiconductor memory structure of claim 1 , wherein the vertically oriented semiconductor memory cell comprises two vertically and serially connected transistors and a shared serially connected capacitor in a SOI pillar.
7. The semiconductor memory structure of claim 1 , wherein the vertically oriented semiconductor memory cell comprises:
a first diode;
a first access transistor connected in series to the first diode;
a second access transistor connected in series to the first access transistor;
a third access transistor connected in series to the second access transistor; a fourth access transistor connected in series to the third access transistor; and
a second diode connected in series to the fourth access transistor;
wherein the first diodes the first, second, third, and fourth transistors, and the second diode are formed on the same SOI pillar.
8. A semiconductor memory structure, comprising:
a substrate having electrical devices formed therein, and further having at least one dielectric layer and at least one interconnect layer disposed above the substrate;
a first stackable add-on layer, the first stackable add-on layer including a plurality of vertically oriented semiconductor memory cells disposed within the first stackable add-on layer, the plurality of vertically oriented semiconductor devices separated from each other by dielectric material; and
wherein the stackable add-on layer is bonded to a layer of the substrate that is the greatest distance from the substrate as measured from the bottom surface of the substrate; and
wherein the memory cell is an SRAM having at least one Negative Differential Resistance device.
9. The semiconductor memory structure of claim 8 , wherein the vertically oriented semiconductor memory cell comprises a vertically oriented transistor and a vertically oriented NDR-type Thyristor serially connected to each other.
10. The semiconductor memory structure of claim 9 , wherein the vertically oriented transistor is formed on an SOI pillar and the vertically NDR-type Thyristor is formed on an SOI pillar.
11. The semiconductor memory structure of claim 9 , wherein the vertically oriented transistor and the vertically NDR-type Thyristor are formed on two separated SOI pillars.
12. The semiconductor memory structure of claim 8 , wherein the vertically oriented transistor and the vertically NDR-type Thyristor are formed on the same SOI pillar.
13. A semiconductor memory structure, comprising:
a substrate having electrical devices formed therein, and further having a dielectric layer disposed above the electrical devices;
a stackable add-on layer having a plurality of vertically oriented semiconductor memory cells; and
the stackable add-on layer being bonded to the dielectric layer; and
wherein the memory cells are nonvolatile memory cells having at least one transistor.
14. The semiconductor memory structure of claim 13 , wherein the vertically oriented semiconductor nonvolatile memory cell comprises a vertical transistor having a floating gate and a control gate on a SOI pillar.
15. The semiconductor memory structure of claim 13 , wherein the vertically oriented semiconductor nonvolatile memory cell comprises a vertical transistor having a charge-trapping gate insulator and a gate on a SOI pillar.
16. The semiconductor memory structure of claim 13 , wherein at least two nonvolatile memory cells are vertically oriented and serially connected together and formed with a first SOI pillar.
17. The semiconductor memory structure of claim 16 , wherein the at least two nonvolatile memory cells on the first SOI pillar are serially connected with an interconnect line disposed on a dielectric layer, to a nonvolatile memory cell formed with a second SOI pillar.