# US 10,770,131 B2 · SRAM cell for interleaved wordline scheme

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- Number: US 10,770,131 B2
- Document ID: US10770131B2
- Status: Granted
- Kind: B2
- Application number: 16/376,198
- Filed: 2019-04-05
- Published: 2019-08-01
- Granted: 2020-09-08
- Earliest claimed: 2015-10-19
- Assignees: Taiwan Semiconductor Manufacturing Company, Ltd.
- Applicants: Taiwan Semiconductor Manufacturing Co., Ltd.
- Inventors: Hidehiro Fujiwara; Hung-Jen Liao; Hsien-Yu Pan; Yen-Huei Chen; Mahmut Sinangil
- Web page: https://patentgrep.com/patent/US10770131B2

## CPC

- G11C 11/412: using field-effect transistors only
- G11C 8/14: Word line organisation; Word line lay-out
- G11C 11/418: Address circuits
- G11C 11/419: Read-write [R-W] circuits
- H10B 10/12: {comprising a MOSFET load element}
- G11C: STATIC STORES (semiconductor memory devices H10B)
- H10B: ELECTRONIC MEMORY DEVICES

## Abstract

Some embodiments relate to an SRAM cell layout including upper and lower cell edges and left and right cell edges. A first power rail extends generally in parallel with and lies along the left cell edge or the right cell edge. The first power rail is coupled to a first power supply. A second power rail extends generally in parallel with the first power rail and is arranged equidistantly between the left and right cell edges. A first bitline extends in parallel with the first power rail and the second power rail and is arranged to a first side of the second power rail. A second bitline, which is complementary to the first bitline, extends in parallel with the first power rail and the second power rail and is arranged to a second side of the second power rail.

## Claims

### Claim 1

A static random access memory (SRAM) cell laid out on a semiconductor substrate according to an SRAM cell layout, the SRAM cell layout comprising:
upper and lower cell edges and left and right cell edges corresponding to an outer perimeter of the SRAM cell on the semiconductor substrate;
a first power rail extending in parallel with and lying along the left cell edge or the right cell edge, wherein the first power rail is configured to couple the SRAM cell to a first voltage;
a second power rail extending in parallel with the first power rail and along a midline of the SRAM cell between the left and right cell edges, wherein second power rail is configured to couple the SRAM cell to a second voltage, the second voltage differing from the first voltage;
a gate electrode disposed at a first height over the semiconductor substrate, the gate electrode extending in parallel with the upper and lower cell edges over the SRAM cell and perpendicular to the first and second power rails; and
a first local interconnect line disposed at the first height and extending in parallel with the gate electrode, wherein a first wide or elongated contact extends laterally and continuously from over an upper surface of the gate electrode to over an upper surface of the first local interconnect line to couple the first local interconnect line to the gate electrode.

### Claim 2 (depends on 1)

The SRAM of claim 1, wherein a second contact couples the second power rail to a second local interconnect line, the second contact having a second width that is less than a first width of the first wide or elongated contact, the first width and second width each being measured in a first direction perpendicular to the gate electrode.

### Claim 3 (depends on 2)

The SRAM of claim 2, wherein the second local interconnect line extends in parallel with the first local interconnect line, and the first local interconnect line is disposed to a first side of the gate electrode and the second local interconnect line is to disposed to a second side of the gate electrode, the second side being opposite the first side.

### Claim 4 (depends on 1)

The SRAM of claim 1, further comprising:
a first bitline extending in parallel with the first power rail and the second power rail and arranged to a first side of the second power rail; and
a second bitline, which is complementary to the first bitline, extending in parallel with the first power rail and the second power rail and arranged to a second side of the second power rail, the second side being opposite the first side.

### Claim 5 (depends on 1)

The SRAM of claim 1, wherein the first power rail is configured to carry a VSS signal and the second power rail is configured to carry a VDD signal.

### Claim 6 (depends on 1)

The SRAM of claim 1, further comprising:
a first wordline and a second wordline extending generally in parallel with the upper and lower cell edges over the SRAM cell and extending perpendicular to the first and second power rails.

### Claim 7 (depends on 6)

The SRAM of claim 6, wherein the first wordline is disposed directly over and in parallel with the gate electrode.

### Claim 8 (depends on 6)

The SRAM of claim 6, wherein the first local interconnect line extends in parallel with the first wordline and the second wordline, and extends between the first wordline and the second wordline.

### Claim 9 (depends on 6)

The SRAM of claim 6, wherein the first wordline and the second wordline are each a metal2 line.

### Claim 10 (depends on 6)

The SRAM of claim 6, wherein only one of the first wordline and the second wordline is coupled to gates of respective access transistors within the SRAM cell.

### Claim 11 (depends on 6)

The SRAM of claim 6, wherein the second power rail is disposed in a metal 1 layer at a first height over the semiconductor substrate, and the first wordline and the second wordline are each disposed in a metal 2 layer at a second height over the semiconductor substrate, the second height being greater than the first height.

### Claim 12

A static random access memory (SRAM) cell laid out on a semiconductor substrate according to an SRAM cell layout, the SRAM cell layout comprising:
upper and lower cell edges and left and right cell edges corresponding to an outer perimeter of the SRAM cell on the semiconductor substrate;
a first power rail extending in parallel with and lying along the left cell edge or the right cell edge, wherein the first power rail is configured to couple the SRAM cell to a first voltage; and
a second power rail extending in parallel with the first power rail and along a midline of the SRAM cell between the left and right cell edges, wherein the second power rail is configured to couple the SRAM cell to a second voltage, the second voltage differing from the first voltage;
two wordlines extending in parallel with the upper and lower cell edges from the midline to a left or right cell edge of the SRAM cell and extending perpendicular to the first and second power rails;
a local interconnect line extending in parallel with the two wordlines and spaced between nearest neighboring sidewalls of the two wordlines; and
wherein the SRAM cell layout consists of three transistors between the midline of the SRAM cell and the left cell edge.

### Claim 13 (depends on 12)

The SRAM cell of claim 12, wherein the second power rail is disposed in a metal 1 layer at a first height over the semiconductor substrate, and the two wordlines are each disposed in a metal 2 layer at a second height over the semiconductor substrate, the second height being greater than the first height.

### Claim 14 (depends on 13)

The SRAM cell of claim 13, wherein only one of the two wordlines is coupled to gates of respective access transistors of the SRAM cell.

### Claim 15

A static random access memory (SRAM) cell laid out on a semiconductor substrate according to an SRAM cell layout, the SRAM cell layout comprising:
upper and lower cell edges and left and right cell edges corresponding to an outer perimeter of the SRAM cell on the semiconductor substrate;
a first power rail extending in parallel with and lying along the left cell edge or the right cell edge, wherein the first power rail is configured to couple the SRAM cell to a first voltage;
a second power rail extending in parallel with the first power rail and along a midline of the SRAM cell between the left and right cell edges, wherein the second power rail is configured to couple the SRAM cell to a second voltage, the second voltage differing from the first voltage; and
two wordlines extending in parallel with the upper and lower cell edges over the SRAM cell and extending perpendicular to the first and second power rails; and
a first local interconnect line extending in parallel with the two wordlines and spaced between nearest neighboring sidewalls of the two wordlines, wherein the SRAM cell layout consists of six transistors within the outer perimeter of the SRAM cell.

### Claim 16 (depends on 15)

The SRAM cell of claim 15, further comprising
a gate electrode extending under a first of the two wordlines and extending in parallel with the first of the wordlines; and
wherein the first local interconnect line is disposed at the same height as the gate electrode over the semiconductor substrate and extends in parallel with the gate electrode, wherein a wide or elongated contact couples the first local interconnect line to the gate electrode.

### Claim 17 (depends on 16)

The SRAM cell of claim 16, wherein a second contact couples the second power rail to a second local interconnect line, the second contact having a second width that is less than a first width of the wide or elongated contact, the first width and second width each being measured in a first direction perpendicular to the gate electrode.

### Claim 18 (depends on 17)

The SRAM cell of claim 17, wherein the second local interconnect line extends in parallel with the first local interconnect line, and the first local interconnect line is disposed to a first side of the first of the two wordlines and the second local interconnect line is to disposed to a second side of the first of the two wordlines, the second side being opposite the first side.

### Claim 19 (depends on 15)

The SRAM of claim 15, further comprising:
a first bitline extending in parallel with the first power rail and the second power rail and arranged to a first side of the second power rail; and
a second bitline, which is complementary to the first bitline, extending in parallel with the first power rail and the second power rail and arranged to a second side of the second power rail, the second side being opposite the first side.

### Claim 20 (depends on 15)

The SRAM cell of claim 15:
wherein the SRAM cell includes first and second access transistors and a pair of cross-coupled inverters, wherein the first and second access transistors allow selective access to complementary storage nodes of the pair of cross-coupled inverters; and
wherein the first and second access transistors include each include a pair of semiconductor fins running parallel to one another and a conductive gate electrode that straddles both semiconductor fins of the pair of semiconductor fins.