Embodiments of the present invention provide a semiconductor structure having a strain relaxed buffer, and method of fabrication. A strain relaxed buffer is disposed on a semiconductor substrate. A silicon region and silicon germanium region are disposed adjacent to each other on the strain relaxed buffer. An additional region of silicon or silicon germanium provides quantum well isolation.

A device includes a semiconductor substrate, and isolation regions extending into the semiconductor substrate. A semiconductor fin is between opposite portions of the isolation regions, wherein the semiconductor fin is over top surfaces of the isolation regions. A gate stack overlaps the semiconductor fin. A source/drain region is on a side of the gate stack and connected to the semiconductor fin. The source/drain region includes an inner portion thinner than the semiconductor fin, and an outer portion outside the inner portion. The semiconductor fin and the inner portion of the source/drain region have a same composition of group IV semiconductors.

A device includes a semiconductor substrate, and isolation regions extending into the semiconductor substrate. A semiconductor fin is between opposite portions of the isolation regions, wherein the semiconductor fin is over top surfaces of the isolation regions. A gate stack overlaps the semiconductor fin. A source/drain region is on a side of the gate stack and connected to the semiconductor fin. The source/drain region includes an inner portion thinner than the semiconductor fin, and an outer portion outside the inner portion. The semiconductor fin and the inner portion of the source/drain region have a same composition of group IV semiconductors.

Middle-of-line (MOL) interconnects that facilitate reduced capacitance and/or resistance and corresponding techniques for forming the MOL interconnects are disclosed herein. An exemplary MOL interconnect structure includes a device-level contact disposed in a first insulator layer and a ruthenium structure disposed in a second insulator layer disposed over the first insulator layer. The device-level contact physically contacts an integrated circuit feature, and the ruthenium structure physically contacts the device-level contact. An air gap separates sidewalls of the ruthenium structure from the second insulator layer. A top surface of the ruthenium structure is lower than a top surface of the second insulator layer. A via disposed in a third insulator layer extends below the top surface of the second insulator layer to physically contact the ruthenium structure. A remainder of a dummy contact spacer layer may separate the first insulator layer and the second insulator layer.

A semiconductor structure and a method for forming the semiconductor structure are provided. The semiconductor structure includes a substrate and a gate structure on the substrate. The substrate contains source-drain openings on both sides of the gate structure. The semiconductor structure also includes a first stress layer formed in a source-drain opening of the source-drain openings. The first stress layer is doped with first ions. In addition, the semiconductor structure includes a protection layer over the first stress layer, and an inversion layer between the first stress layer and the protection layer. The protection layer is doped with second ions, and the inversion layer is doped with third ions. A conductivity type of the third ions is opposite to a conductivity type of the second ions.

A semiconductor structure and a method for forming the semiconductor structure are provided. The semiconductor structure includes a substrate and a gate structure on the substrate. The substrate contains source-drain openings on both sides of the gate structure. The semiconductor structure also includes a first stress layer formed in a source-drain opening of the source-drain openings. The first stress layer is doped with first ions. In addition, the semiconductor structure includes a protection layer over the first stress layer, and an inversion layer between the first stress layer and the protection layer. The protection layer is doped with second ions, and the inversion layer is doped with third ions. A conductivity type of the third ions is opposite to a conductivity type of the second ions.

A semiconductor structure includes a substrate, first fins extending from the substrate with a first fin pitch, and second fins extending from the substrate with a second fin pitch smaller than the first fin pitch. The semiconductor structure also includes first gate structures engaging the first fins with a first gate pitch and second gate structures engaging the second fins with a second gate pitch smaller than the first gate pitch. The semiconductor structure also includes first epitaxial semiconductor features partially embedded in the first fins and adjacent the first gate structures and second epitaxial semiconductor features partially embedded in the second fins and adjacent the second gate structures. A bottom surface of the first epitaxial semiconductor features is lower than a bottom surface of the second epitaxial semiconductor features.

A semiconductor structure includes a substrate, first fins extending from the substrate with a first fin pitch, and second fins extending from the substrate with a second fin pitch smaller than the first fin pitch. The semiconductor structure also includes first gate structures engaging the first fins with a first gate pitch and second gate structures engaging the second fins with a second gate pitch smaller than the first gate pitch. The semiconductor structure also includes first epitaxial semiconductor features partially embedded in the first fins and adjacent the first gate structures and second epitaxial semiconductor features partially embedded in the second fins and adjacent the second gate structures. A bottom surface of the first epitaxial semiconductor features is lower than a bottom surface of the second epitaxial semiconductor features.

A method for integrating transistors and anti-fuses on a device includes epitaxially growing a semiconductor layer on a substrate and masking a transistor region of the semiconductor layer. An oxide is formed on an anti-fuse region of the semiconductor layer. A semiconductor material is grown over the semiconductor layer to form an epitaxial semiconductor layer in the transistor region and a defective semiconductor layer in the anti-fuse region. Transistor devices in the transistor region and anti-fuse devices in the anti-fuse region are formed wherein the defective semiconductor layer is programmable by an applied field.

A method for integrating transistors and anti-fuses on a device includes epitaxially growing a semiconductor layer on a substrate and masking a transistor region of the semiconductor layer. An oxide is formed on an anti-fuse region of the semiconductor layer. A semiconductor material is grown over the semiconductor layer to form an epitaxial semiconductor layer in the transistor region and a defective semiconductor layer in the anti-fuse region. Transistor devices in the transistor region and anti-fuse devices in the anti-fuse region are formed wherein the defective semiconductor layer is programmable by an applied field.