A semiconductor device includes a gate positioned on a substrate; a nanosheet that extends through the gate, protrudes from a sidewall of the gate, and forms a recess between the substrate and the nanosheet; a dielectric spacer disposed in the recess; a source/drain contact positioned on a source/drain disposed on the substrate adjacent to the gate; an air gap spacer positioned along the sidewall of the gate and in contact with a dielectric material disposed on the nanosheet, the air gap spacer being in contact with the source/drain contact; and an interlayer dielectric (ILD) disposed on the air gap spacer.

A semiconductor device includes a substrate having a fin projecting upwardly through an isolation structure over the substrate; a gate stack over the isolation structure and engaging the fin; and a gate spacer on a sidewall of the gate stack and in physical contact with the gate stack. The semiconductor device further includes a first dielectric layer vertically between the fin and the gate spacer and in physical contact with the sidewall of the gate stack, wherein the first dielectric layer has a laterally extending cavity. The semiconductor device further includes a second dielectric layer filling in the cavity, wherein the first and second dielectric layers include different materials.

A method for forming a semiconductor device includes forming a first fin and a second fin on a substrate, the first fin arranged in parallel with the second fin, the first fin arranged a first distance from the second fin, the first fin and the second fin extending from a first source/drain region through a channel region and into a second source/drain region on the substrate. The method further includes forming a third fin on the substrate, the third fin arranged in parallel with the first fin and between the first fin and the second fin, the third fin arranged a second distance from the first fin, the second distance is less than the first distance, the third fin having two distal ends arranged in the first source/drain region. A gate stack is formed over the first fin and the second fin.

A method of forming a spacer for a vertical transistor is provided. The method includes forming a fin structure that includes a fin on a semiconductor substrate, forming a source junction or a drain junction at an upper surface of the semiconductor substrate and at a base of the fin and epitaxially growing a rare earth oxide (REO) spacer to have a substantially uniform thickness along respective upper surfaces of the source or drain junction and on opposite sides of the fin structure.

A semiconductor device including at least one fin extending upward from a substrate and a gate on the substrate, wherein the gate includes outer sidewalls, wherein the fin extend through a width of the gate. A spacer material can be adjacent to the outer sidewalls of the gate, wherein a top surface of the spacer material is below the top surface of the gate and above the top surface of the fin. The semiconductor device can also include an epitaxial semiconductor layer over the fins on each side of the spacer material. A low-k dielectric material can be deposited above each epitaxial semiconductor layer. The semiconductor device also includes a dielectric top layer forming a top surface of the transistor, wherein the dielectric top layer seals an air gap between the top surface of the fins and the dielectric top layer.

A semiconductor device including at least one fin extending upward from a substrate and a gate on the substrate, wherein the gate includes outer sidewalls, wherein the fin extend through a width of the gate. A spacer material can be adjacent to the outer sidewalls of the gate, wherein a top surface of the spacer material is below the top surface of the gate and above the top surface of the fin. The semiconductor device can also include an epitaxial semiconductor layer over the fins on each side of the spacer material. A low-k dielectric material can be deposited above each epitaxial semiconductor layer. The semiconductor device also includes a dielectric top layer forming a top surface of the transistor, wherein the dielectric top layer seals an air gap between the top surface of the fins and the dielectric top layer.

A semiconductor device includes a semiconductor substrate, a gate structure formed over the semiconductor substrate, and an epitaxial structure formed partially within the semiconductor substrate. A vertically extending portion of the epitaxial structure extends vertically above a top surface of the semiconductor substrate in an area adjacent the gate structure. A laterally extending portion of the epitaxial structure extends laterally at an area below the top surface of the semiconductor substrate in a direction toward an area below the gate structure and beyond an area where the epitaxial structure extends vertically. The device further includes an interlayer dielectric layer between a side surface of the vertically extending portion of the epitaxial structure and a side surface of the gate structure. A top surface of the laterally extending portion of the epitaxial structure directly contacts the interlayer dielectric layer.

A method to form a semiconductor structure with an active region and a compatible dielectric layer is described. In one embodiment, a semiconductor structure has a dielectric layer comprised of an oxide of a first semiconductor material, wherein a second (and compositionally different) semiconductor material is formed between the dielectric layer and the first semiconductor material. In another embodiment, a portion of the second semiconductor material is replaced with a third semiconductor material in order to impart uniaxial strain to the lattice structure of the second semiconductor material.

Semiconductor devices with airgap spacers and methods of forming the same include forming a lower spacer that defines a gate region. A sacrificial upper spacer is formed directly above the lower spacer. A gate stack is formed in the gate region. The sacrificial upper spacer is etched away to form an upper spacer opening. An airgap spacer is formed in the upper spacer opening. The airgap spacer includes a dielectric material that encapsulates an internal void.

After forming a sacrificial gate structure straddling a stacking of a semiconductor mandrel structure and a dielectric mandrel cap and spacers present on sidewalls of the stack, portions of the spacers located on opposite sides of the sacrificial gate structure are removed. Epitaxial source/drain regions are formed on exposed sidewalls of portions of the semiconductor mandrel structure located on opposite sides of the sacrificial gate structure. The sacrificial gate structure is removed to provide a gate cavity. Next, portions of the spacers exposed by the gate cavity are removed to expose sidewalls of a portion of the semiconductor mandrel structure. III-V compound semiconductor channel portions are then formed on exposed sidewalls of the semiconductor mandrel structure. Portions of the semiconductor mandrel structure and the dielectric mandrel cap exposed by the gate cavity are subsequently removed from the structure, leaving only the III-V compound semiconductor channel portions.