Semiconductor device including a layer between a source/drain region and a substrate
View Patent ↗Devices and methods are described herein that obviate the need for a read assist circuit. In one example, a semiconductor device includes a source region and a drain region formed above a substrate. A buried insulator (BI) layer is formed beneath either the source region or the drain region. A first nano-sheet is formed (i) horizontally between the source region and the drain region and (ii) vertically above the BI layer. The BI layer reduces current flow through the first nano-sheet.
1. A semiconductor device comprising:
a first transistor above a substrate and including:
a first source/drain region;
a layer between the first source/drain region and the substrate and made of a dielectric material, wherein the first source/drain region and the layer are along a first direction;
a second source/drain region in contact with the substrate, wherein the first and second source/drain regions are along a second direction transverse to the first direction; and
a channel region in contact with the substrate.
2. The semiconductor device of claim 1 , further comprising a gate electrode on top and bottom surfaces of the channel region.
3. The semiconductor device of claim 1 , wherein the channel region includes a plurality of nano-sheets.
4. The semiconductor device of claim 3 , wherein each of the nano-sheets has a sheet width and the layer has a width substantially equal to or greater than the sheet width.
5. The semiconductor device of claim 1 , wherein the first transistor includes a gate and the layer has a depth greater than half of a depth of the gate.
6. The semiconductor device of claim 1 , further comprising a second transistor adjacent the first transistor, wherein the layer has a length substantially equal to or greater than a space between a gate of the first transistor and a gate of the second transistor.
7. The semiconductor device of claim 1 , wherein a top surface of the substrate is at least one of above a bottom surface of the layer and substantially aligned with a top surface of the layer.
8. The semiconductor device of claim 1 , further comprising an inverter connected to the second source/drain region of the first transistor and including a second transistor, wherein the first and second transistors are configured such that a current flowing through the second transistor is greater than a current that flows through the first transistor.
9. A memory device comprising:
a plurality of bitcells, each bitcell including:
a first transistor above a substrate and having
a first source/drain region,
a first layer between the first source/drain region and the substrate and made of a different material than the substrate, wherein the first source/drain region and the first layer are along a first direction,
a second source/drain region in contact with the substrate, wherein the first and second source/drain regions are along a second direction transverse to the first direction, and
a channel region in contact with the substrate; and
a first bitline coupled to the first source/drain region of the first transistor.
10. The memory device of claim 9 , wherein the channel region is between the first source/drain region and the second source/drain region and is above a topmost surface of the substrate.
11. The memory device of claim 9 , further comprising a gate electrode on top and bottom surfaces of the channel region.
12. The memory device of claim 9 , further comprising an inverter connected to the second source/drain region of the first transistor.
13. The memory device of claim 9 , wherein each bitcell further includes:
a second transistor above the substrate and having
a first source/drain region,
a second layer between the first source/drain region and the substrate and made of a different material than the substrate, and
a second source/drain region in contact with the substrate; and
a second bitline coupled to the first source/drain region of the second transistor.
14. The memory device of claim 13 , further comprising an inverter connected to the second source/drain region of the second transistor.
15. The memory device of claim 13 , wherein each of the first and second transistors has a gate connected to a wordline.
16. A method comprising:
generating a first current that flows through a first transistor of a bitcell, the first transistor having a first source/drain region connected to a bit line of the bitcell; and
generating a second current that is greater than the first current and that flows through a second transistor of the bitcell, the second transistor being connected to a second source/drain region of the first transistor.
17. The method of claim 16 , further comprising performing a read operation on the bitcell without requiring read assist circuitry.
18. The method of claim 16 , wherein the second transistor is further connected to a third transistor and the second and third transistors form an inverter.
19. The method of claim 16 , wherein the first transistor has a gate connected to a wordline.
20. The method of claim 16 , wherein the bitcell further comprises an inverter that includes the second transistor.