A device includes a fin extending from a substrate; a gate stack over and along sidewalls of the fin; a gate spacer along a sidewall of the gate stack; an epitaxial source/drain region in the fin and adjacent the gate spacer, the epitaxial source/drain region including a first epitaxial layer on the fin, the first epitaxial layer including silicon and arsenic; and a second epitaxial layer on the first epitaxial layer, the second epitaxial layer including silicon and phosphorus, the first epitaxial layer separating the second epitaxial layer from the fin; and a contact plug on the second epitaxial layer.

A semiconductor structure and a method for forming the same are provided. The semiconductor structure includes a gate structure formed over a fin structure, and a source/drain (S/D) epitaxial layer formed in the fin structure and adjacent to the gate structure. The S/D epitaxial layer includes a first S/D epitaxial layer and a second epitaxial layer. The semiconductor structure includes a gate spacer formed on a sidewall surface of the gate structure, and the gate spacer is directly over the first S/D epitaxial layer. The semiconductor structure includes a dielectric spacer formed adjacent to the gate spacer, and the dielectric spacer is directly over the second epitaxial layer.

A device includes a semiconductor substrate, a first fin arranged over the semiconductor substrate, and an isolation structure. The first fin includes an upper portion, a bottom portion, and an insulator layer between the upper portion and the bottom portion. A top surface of the insulator layer is wider than a bottom surface of the upper portion of the first fin. The isolation structure surrounds the bottom portion of the first fin.

Doping techniques for fin-like field effect transistors (FinFETs) are disclosed herein. An exemplary method includes forming a fin structure, forming a doped amorphous layer over a portion of the fin structure, and performing a knock-on implantation process to drive a dopant from the doped amorphous layer into the portion of the fin structure, thereby forming a doped feature. The doped amorphous layer includes a non-crystalline form of a material. In some implementations, the knock-on implantation process crystallizes at least a portion of the doped amorphous layer, such that the portion of the doped amorphous layer becomes a part of the fin structure. In some implementations, the doped amorphous layer includes amorphous silicon, and the knock-on implantation process crystallizes a portion of the doped amorphous silicon layer.

The present disclosure describes a method to form silicon germanium (SiGe) source/drain epitaxial stacks with a boron doping profile and a germanium concentration that can induce external stress to a fully strained SiGe channel. The method includes forming one or more gate structures over a fin, where the fin includes a fin height, a first sidewall, and a second sidewall opposite to the first sidewall. The method also includes forming a first spacer on the first sidewall of the fin and a second spacer on the second sidewall of the fin; etching the fin to reduce the fin height between the one or more gate structures; and etching the first spacer and the second spacer between the one or more gate structures so that the etched first spacer is shorter than the etched second spacer and the first and second etched spacers are shorter than the etched fin. The method further includes forming an epitaxial stack on the etched fin between the one or more gate structures.

A method of processing a substrate that includes: loading the substrate in a processing chamber, the substrate including a raised feature of a semiconductor; forming a conformal dopant layer on the raised feature by atomic layer deposition (ALD); forming a metal layer over the raised feature; thermally treating the dopant layer to form an ultra-shallow dopant region in the raised feature by diffusion of a dopant from the dopant layer into the raised feature; and thermally treating the metal layer to form an ohmic contact region in the raised feature by diffusion of a metal from the metal layer into the raised feature.

A device includes a fin extending from a substrate; a gate stack over and along sidewalls of the fin; a gate spacer along a sidewall of the gate stack; an epitaxial source/drain region in the fin and adjacent the gate spacer, the epitaxial source/drain region including a first epitaxial layer on the fin, the first epitaxial layer including silicon and arsenic; and a second epitaxial layer on the first epitaxial layer, the second epitaxial layer including silicon and phosphorus, the first epitaxial layer separating the second epitaxial layer from the fin; and a contact plug on the second epitaxial layer.

A semiconductor structure and its fabrication method are provided in the present disclosure. The method includes providing a layer to-be-etched, including first regions and second regions. The method further includes forming a plurality of discrete first sacrificial layers on the layer to-be-etched, where a plurality of openings is between the plurality of first sacrificial layers and includes first openings on the first regions. The method further includes forming initial sidewall spacer structures on sidewalls of the plurality of first sacrificial layers, where the initial sidewall spacer structures include first sidewall spacers, and the first sidewall spacers fill the first openings. The method further includes, using the first sidewall spacers as an alignment mark, forming a first mask layer on the layer to-be-etched and the initial sidewall spacer structures, where the first mask layer exposes a portion of the layer to-be-etched and a portion of the initial sidewall spacer structures.

A semiconductor device includes a fin structure over a substrate. The fin structure includes a bottom portion and a top portion. The bottom and the top portions have different materials. The device also includes a liner layer on a sidewall of the bottom portion, a dielectric layer on side surfaces of the liner layer, an interfacial layer, and a gate structure over the dielectric layer and engages the fin structure. A top surface of the liner layer extends below a bottom surface of the top portion. The interfacial layer has a first section on and directly contacting sidewall surfaces of the bottom portion and a second section on and directly contacting top and sidewall surfaces of the top portion. The gate structure includes a high-k dielectric layer and a metal gate electrode over the high-k dielectric layer. The high-k dielectric layer directly contacts the first section of the interfacial layer.

A semiconductor device includes a substrate, a plurality of fins on the substrate, and an isolation region between the fins. Each of the fins includes a semiconductor material region and an impurity region disposed in the semiconductor material region. The impurity region has an upper surface below an upper surface of the isolation region.