Nanosheet transistors with transverse strained channel regions

1. A method of fabricating a semiconductor device, the method comprising:

forming a nanosheet stack on a substrate;

wherein the nanosheet stack comprises nanosheet channel layers;

forming a gate around the nanosheet channel layers of the nanosheet stack; and

forming a strained material along a sidewall surface of the gate;

wherein the strained material is configured to create strain in the channel nanosheet layers of the nanosheet stack, wherein the strain in the channel nanosheet layers is created in a strain direction that is transverse to a carrier transport direction in the channel nanosheet layers, and wherein the strain direction is parallel to a lateral surface of the nanosheet stack; and forming the strained material along the sidewall surface of the gate comprises: removing a portion of the gate to form a trench, wherein a portion of the trench is defined by sidewall surface of the gate; and depositing the strained material in the trench.

2. The method of claim 1 , wherein the nanosheet stack comprises:

sacrificial layers; and

material of the sacrificial layers is structured to be selectively etched.

3. The method of claim 1 , wherein forming the gate comprises:

forming a sacrificial dummy gate on the nanosheet stack; and

replacing the sacrificial dummy gate with a conductive replacement gate material comprising the gate.

4. The method of claim 3 further comprising forming an offset spacer positioned along a sidewall of the sacrificial dummy gate before replacing the sacrificial dummy gate with the conductive replacement gate material.

5. The method of claim 2 further comprising:

removing an end portion of at least one of the sacrificial layers of the nanosheet stack to form a cavity; and

depositing an inner spacer material in the cavity.

6. The method of claim 1 , wherein the strained material comprises tensile strained silicon nitride.

7. The method of claim 1 , wherein a depth of the trench comprises from about 50 to about 150 nm.

8. The method of claim 1 , wherein the strain created in the channel nanosheet layers of the nanosheet stack comprises from about 0.1 to about 2 GPa.

9. A method of fabricating a semiconductor device, the method comprising:

forming a pFET portion and a nFET portion on a substrate;

forming a gate around the pFET portion and the nFET portion;

forming a first trench by removing a portion of the gate material from the pFET portion;

forming a second trench by removing a portion of the gate material from the nFET portion;

forming a strained material in the first and the second trenches.

10. The method of claim 9 further comprising forming a shallow trench isolation (STI) region in the substrate.

11. A method of fabricating a semiconductor device, the method comprising:

forming an nFET gate over a first nanosheet channel;

forming a pFET gate over a second nanosheet channel; and

forming a tensile strained material on a sidewall of the nFET gate and on a sidewall of the pFET gate;

wherein the tensile strained material is configured to create strain in the first and second nanosheet channels, wherein the strain is transverse to a carrier transport direction, and wherein a strain direction in the first nanosheet channel is opposite a strain direction in the second nanosheet channel; and forming the tensile strained material comprises: removing a portion of the nFET gate to form a first trench, wherein a portion of the first trench is defined by a sidewall surface of the nFET gate; removing a portion of the pFET gate to form a second trench, wherein a portion of the second trench is defined by a sidewall surface of the pFET gate; and depositing the tensile strained material in the first trench and the second trench.