A semiconductor structure is provided. The semiconductor structure includes an epitaxial structure over a semiconductor substrate. The semiconductor structure also includes a conductive feature over the semiconductor substrate. The conductive feature includes a high-k dielectric layer and a metal layer on the high-k dielectric layer, and a top surface of the metal layer is below a top surface of the high-k dielectric layer. The semiconductor structure further includes a metal-semiconductor compound layer formed on the epitaxial structure. In addition, the semiconductor structure includes a first metal contact structure formed on the top surface of the metal layer of the conductive feature. The semiconductor structure further includes a second metal contact structure formed on the metal-semiconductor compound layer.

A semiconductor structure includes a substrate and a first field effect transistor (FET) formed on the substrate; the first FET includes a first FET first source-drain region, a first FET second source-drain region, a first FET gate between the first and second source-drain regions, and a first FET channel region adjacent the first FET gate and between the first FET first and second source-drain regions. Also included is a buried power rail, buried in the substrate, having a top at a level lower than the first FET channel region, and having buried power rail sidewalls. A first FET shared contact is electrically interconnected with the buried power rail and the first FET second source-drain region, and a first FET electrically isolating region is adjacent the buried power rail sidewalls and separates the buried power rail from the substrate.

Embodiments disclosed herein describe methods of forming semiconductor devices. The methods may include etching vias and trenches in a middle-of-line (MOL) layer that has a low-k dielectric layer, a sacrificial nitride layer, and a hard mask layer. The methods may also include depositing a thin nitride layer within the via trench, depositing a carbon layer on the thin nitride layer within the vias and trenches, etching back the thin nitride layer to expose a portion of the hard mask layer, removing the hard mask layer and the carbon layer, and removing the thin nitride layer and the sacrificial nitride layer.

The present disclosure provides example embodiments relating to conductive features, such as metal contacts, vias, lines, etc., and methods for forming those conductive features. In an embodiment, portions of an adhesion layer, barrier layer and/or seed layer is protected by a layer of an organic mask material as portions of the adhesion layer, barrier layer and/or seed layer are removed. The layer of organic mask material is modified to improve its resistance to penetration by wet etchants used to remove exposed portions of the adhesion layer, barrier layer and/or seed layer. An example modification includes treating the layer of organic mask material with a surfactant that is absorbed into the layer of organic mask material.

Methods and devices including an air gap adjacent a contact element extending to a source/drain feature of a device are described. Some embodiments of the method include depositing a dummy layer, which is subsequently removed to form the air gap. The dummy layer and subsequent air gap may be formed after a SAC dielectric layer such as silicon nitride is formed over an adjacent metal gate structure.

A blocking material is selectively deposited on a bottom surface of a back end of line (BEOL) conductive structure such that a barrier layer is selectively deposited on sidewalls of the BEOL conductive structure but not the bottom surface. The blocking material is etched such that copper from a conductive structure underneath is exposed, and a ruthenium layer is deposited on the barrier layer but less ruthenium is deposited on the exposed copper. Accordingly, the barrier layer prevents diffusion of metal ions from the BEOL conductive structure and is substantially absent from the bottom surface as compared to the sidewalls in order to reduce contact resistance. Additionally, the ruthenium layer reduces surface roughness within the BEOL conductive structure and is thinner at the bottom surface as compared to the sidewalls in order to reduce contact resistance.

Interconnect structures and method of forming the same are disclosed herein. An exemplary interconnect structure includes a first contact feature in a first dielectric layer, a second dielectric layer over the first dielectric layer, a second contact feature over the first contact feature, a barrier layer between the second dielectric layer and the second contact feature, and a liner between the barrier layer and the second contact feature. An interface between the first contact feature and the second contact feature includes the liner but is free of the barrier layer.

In an embodiment, a device includes: a gate electrode; a epitaxial source/drain region adjacent the gate electrode; one or more inter-layer dielectric (ILD) layers over the epitaxial source/drain region; a first source/drain contact extending through the ILD layers, the first source/drain contact connected to the epitaxial source/drain region; a contact spacer surrounding the first source/drain contact; and a void disposed between the contact spacer and the ILD layers.

A method includes providing a substrate including metal gate stacks and source/drain contact regions in alternating arrangement along a surface of the substrate with a dielectric spacer separating each source/drain contact region from adjacent metal gate stacks. Each source/drain region is recessed within an opening between adjacent metal gate stacks such that source/drain contact regions provide a bottom of the recess and dielectric spacers provide sidewalls. The etch stop layer is formed on the substrate such that it conformally covers the metal gate stacks, the sidewalls and the bottom of each recess, and a sacrificial layer is formed over each of the metal gate stacks and on at least a portion of each sidewall. The etch stop layer is removed from the bottom of each recess to expose the source/drain contact, and the sacrificial layer is then removed from the metal gate stacks and the sidewalls of each recess.

A transistor structure includes a layer of active material on a base. The base can be insulator material in some cases. The layer has a channel region between a source region and a drain region. A gate structure is in contact with the channel region and includes a gate electrode and a gate dielectric, where the gate dielectric is between the gate electrode and the active material. An electrical contact is on one or both of the source region and the drain region. The electrical contact has a larger portion in contact with a top surface of the active material and a smaller portion extending through the layer of active material into the base. The active material may be, for example, a transition metal dichalcogenide (TMD) in some embodiments.