FinFET SRAM cells with dielectric fins

1. An integrated circuit (IC), comprising:

a first static random access memory (SRAM) cell oriented lengthwise along a first direction and widthwise along a second direction generally perpendicular to the first direction, wherein the first SRAM cell is disposed over a substrate, and wherein the first SRAM cell includes:

first, second, third, and fourth dielectric fins disposed in this order along the first direction and oriented lengthwise along the second direction, wherein the first and the fourth dielectric fins define two edges of the first SRAM cell, and wherein bottom portions of the first, second, third, and fourth dielectric fins are disposed in isolation features over the substrate;

a first p-type semiconductor fin disposed between the first and the second dielectric fins;

a second p-type semiconductor fin disposed between the third and the fourth dielectric fins;

a first n-type semiconductor fin and a second n-type semiconductor fin disposed between the second and the third dielectric fins,

wherein the first and the second p-type semiconductor fins and the first and the second n-type semiconductor fins are oriented lengthwise along the second direction, and

wherein the isolation features separate each of the first and the second p-type semiconductor fins and the first and the second n-type semiconductor fins from each of the first, second, third, and fourth dielectric fins; and

gate structures oriented lengthwise along the first direction and spaced from each other along the second direction, wherein the gate structures engage one or more of the first, the second, the third, and the fourth dielectric fin, the first and the second n-type semiconductor fins, and the first and the second p-type semiconductor fins.

2. The IC of claim 1 , further comprising:

a second SRAM cell disposed next to the first SRAM cell along the second direction, wherein layout of the second SRAM cell is a mirror image of layout of the first SRAM cell with respect to a first imaginary boundary line in the first direction;

a third SRAM cell disposed next to the second SRAM cell along the first direction, wherein layout of the third SRAM cell is a mirror image of the layout of the second SRAM cell with respect to a second imaginary boundary line going through the fourth dielectric fin lengthwise; and

a fourth SRAM cell disposed next to the third SRAM cell along the second direction and next to the first SRAM cell along the first direction, wherein layout of the fourth SRAM cell is a mirror image of the layout of the first SRAM cell with respect to the second imaginary boundary line.

3. The IC of claim 1 , wherein only one p-type semiconductor fin is disposed between the first and the second dielectric fins and between the third and the fourth dielectric fins.

4. The IC of claim 1 , further comprising a third p-type semiconductor fin disposed between the first and the second dielectric fins and a fourth p-type semiconductor fin disposed between the third and the fourth dielectric fins, wherein the isolation features separate the third and the fourth p-type semiconductor fins from each of the first, second, third, and fourth dielectric fins.

5. The IC of claim 1 , further comprising an n-type source/drain (S/D) epitaxial feature disposed over a portion of each of the first and the second p-type semiconductor fins and a p-type S/D epitaxial feature disposed over a portion of each of the first and the second n-type semiconductor fins.

6. The IC of claim 5 , wherein a first S/D contact is disposed over and physically contacts the S/D epitaxial feature over the first p-type semiconductor fin, the S/D epitaxial feature over the first n-type semiconductor fin, and the second dielectric fin, and wherein a second S/D contact is disposed over and physically contacts the S/D epitaxial feature over the second p-type semiconductor fin, the S/D epitaxial feature over the second n-type semiconductor fin, and the fourth dielectric fin.

7. The IC of claim 1 , wherein each of the first, the second, the third, and the fourth dielectric fins includes silicon oxide, silicon oxycarbide, silicon oxynitride, silicon oxycarbonitride, titanium oxide, zirconium oxide, aluminum oxide, yttrium oxide, or combinations thereof.

8. The IC of claim 1 , wherein portions of the first, the second, the third, and the fourth dielectric fins directly under the gate structures have a first height, and wherein portions of the first, the second, the third, and the fourth dielectric fin not under the gate structures have a second height, the first height being greater than the second height.

9. A semiconductor device, comprising:

first, second, third, and fourth static random access memory (SRAM) cells arranged clockwise in a grid, the grid being oriented lengthwise in a first direction and widthwise in a second direction generally perpendicular to the first direction, wherein the first SRAM cell is disposed on a bottom-left corner of the grid and the second SRAM cell is disposed next to the first SRAM cell along the second direction, and wherein the third and the fourth SRAM cells are mirror images of the second and the first SRAM cells, respectively, about the second direction, each of the first, the second, the third, and the fourth SRAM cells including:

a first p-type semiconductor fin disposed between a first boundary dielectric fin and a first inner dielectric fin;

a first and a second n-type semiconductor fins disposed between the first inner dielectric fin and a second inner dielectric fin;

a second p-type semiconductor fin disposed between the second inner dielectric fin and a second boundary dielectric fin;

source/drain (S/D) epitaxial features each disposed over each of the first and the second p-type semiconductor fins and the first and the second n-type semiconductor fins;

a first S/D contact disposed over and physically contacting the S/D epitaxial feature over the first p-type semiconductor fin, the S/D epitaxial feature over the first n-type semiconductor fin, and the first inner dielectric fin; and

a second S/D contact disposed over and physically contacting the S/D epitaxial feature over the second p-type semiconductor fin, the S/D epitaxial feature over the second n-type semiconductor fin, and the second inner dielectric fin,

wherein the first and the second boundary dielectric fins, the first and the second inner dielectric fins, the first and the second p-type semiconductor fins, and the first and the second n-type semiconductor fins are oriented lengthwise along the second direction, and wherein the first and the second S/D contacts are oriented lengthwise along the first direction.

10. The semiconductor device of claim 9 , in a cross-sectional view through the first S/D contact lengthwise, wherein a widest portion of the S/D epitaxial feature over the first p-type semiconductor fin and a widest portion of the S/D epitaxial feature over the first n-type semiconductor fin physically contact the first inner dielectric fin.

11. The semiconductor device of claim 9 , in a cross-sectional view through the second S/D contact lengthwise, wherein a top surface of the second inner dielectric fin is substantially coplanar with the widest portion of the S/D epitaxial feature over the second n-type semiconductor fin and the widest portion of the S/D epitaxial feature over the second p-type semiconductor fin.

12. The semiconductor device of claim 9 , in a cross-sectional view through the first S/D contact lengthwise, wherein a top surface of the first inner dielectric fin is below a widest portion of the S/D epitaxial feature over the first p-type semiconductor fin and a widest portion of the S/D epitaxial feature over the first n-type semiconductor fin.

13. The semiconductor device of claim 9 , in a cross-sectional view through the first and the second S/D contacts lengthwise, wherein a top surface of each of the first and the second boundary dielectric fins is above a top surface of each of the first and the second inner dielectric fins.

14. The semiconductor device of claim 9 , in a cross-sectional view through the first and the second S/D contacts lengthwise, wherein a top surface of each of the first and the second boundary dielectric fins is below a top surface of each of the first and the second inner dielectric fins.

15. The semiconductor device of claim 9 , in a cross-sectional view through the first and the second S/D contacts lengthwise, wherein a top surface of each of the first and the second boundary dielectric fins is substantially coplanar with a top surface of each of the first and the second inner dielectric fins.

16. The semiconductor device of claim 9 , in a cross-sectional view through the first and the second S/D contacts lengthwise, a separation distance between a widest portion of the S/D epitaxial feature over the first n-type semiconductor fin and a widest portion of the S/D epitaxial feature over the second n-type semiconductor fin is less than another separation distance between the widest portion of the S/D epitaxial feature over the first n-type semiconductor fin and a widest portion of the S/D epitaxial feature over the first p-type semiconductor fin.

17. An integrated circuit (IC), comprising:

a first SRAM cell oriented lengthwise along a first direction and widthwise along a second direction generally perpendicular to the first direction, wherein the first SRAM cell includes:

first, second, third, and fourth dielectric fins disposed in this order along the first direction and oriented lengthwise along the second direction, wherein the first and the fourth dielectric fins define two edges of the first SRAM cell, and wherein the first, second, third, and fourth dielectric fins are disposed in isolation structures over a substrate;

a first p-type semiconductor fin disposed between the first and the second dielectric fins;

a second p-type semiconductor fin disposed between the third and the fourth dielectric fins;

a first and a second n-type semiconductor fins disposed between the second and the third dielectric fins,

wherein the first and the second p-type semiconductor fins and the first and the second n-type semiconductor fins are oriented lengthwise along the second direction and separated from each of the first, second, third, and fourth dielectric fins by portions of the isolation structures; and

gate structures oriented lengthwise along the first direction and spaced from each other along the second direction, wherein the gate structures engage the first p-type semiconductor fin to form a first pass-gate (PG) field effect transistor (FET) and a first pull-down (PD) FET, engage the first n-type semiconductor fin to form a first pull-up (PU) FET, engage the second p-type semiconductor fin to form a second PG FET and a second PD FET, and engage the second n-type semiconductor fin to form a second PU FET.

18. The IC of claim 17 , further comprising:

a second SRAM cell disposed next to the first SRAM cell along the second direction, wherein layout of the second SRAM cell is a mirror image of the layout of the first SRAM cell with respect to a first imaginary boundary line in the first direction;

a third SRAM cell disposed next to the second SRAM cell along the first direction, wherein layout of the third SRAM cell is a mirror image of the layout of the second SRAM cell with respect to a second imaginary boundary line going through the fourth dielectric fin lengthwise; and

a fourth SRAM cell disposed next to the third SRAM cell along the second direction and next to the first SRAM cell along the first direction, wherein layout of the fourth SRAM cell is a mirror image of the layout of the first SRAM cell with respect to the second imaginary boundary line.

19. The IC of claim 17 , wherein a space between the first and the second n-type semiconductor fins is free of any dielectric fin.

20. The IC of claim 17 , wherein the first PU FET and the first PD FET are configured to form a first inverter, and wherein the second PU FET and the second PD FET are configured to form a second inverter, the first inverter and the second inverter being cross-coupled.