Semiconductor devices including air spacers formed in a backside interconnect structure and methods of forming the same are disclosed. In an embodiment, a device includes a first transistor structure; a front-side interconnect structure on a front-side of the first transistor structure; and a backside interconnect structure on a backside of the first transistor structure, the backside interconnect structure including a first dielectric layer on the backside of the first transistor structure; a first via extending through the first dielectric layer, the first via being electrically coupled to a source/drain region of the first transistor structure; a first conductive line electrically coupled to the first via; and an air spacer adjacent the first conductive line in a direction parallel to a backside surface of the first dielectric layer.

In a method for forming a semiconductor device, a layer of logic devices is formed on a substrate. The layer of logic devices includes a stack of gate-all-around field-effect transistors (GAA-FETs) positioned over the substrate, where the stack of GAA-FETs includes a first layer of GAA-FETs stacked over a second layer of GAA-FETs. A first wiring layer is formed over the layer of logic devices, where the first wiring layer includes one or more metal routing levels. A memory stack is formed over the first wiring layer. The memory stack includes wordline layers and insulating layers that alternatingly arranged over the first wiring layer. A three-dimensional (3D) NAND memory device is formed in the memory stack. The 3D NAND memory device includes a channel structure that extends into the memory stack and further is coupled to the wordline layers of the memory stack.

A semiconductor device includes a substrate, an isolation structure, a semiconductor fin, a semiconductor layer, and a gate structure. The isolation structure is disposed over the substrate. The semiconductor fin extends from the substrate and in contact with the isolation structure. The semiconductor layer is disposed on and in contact with the isolation structure. The gate structure covers the semiconductor layer and spaced apart from the semiconductor fin.

A semiconductor device is provided that includes a local passthrough interconnect structure present in a non-active device region of the device. A dielectric fill material structure is located between the local passthrough interconnect structure and a functional gate structure that is present in an active device region that is laterally adjacent to the non-active device region. The semiconductor device has reduced capacitance (and thus circuit speed is not compromised) as compared to an equivalent device in which a metal-containing sacrificial gate structure is used instead of the dielectric fill material structure.

A semiconductor device includes a substrate; a fin structure formed on a substrate; and a gate feature formed over the fin structure, the gate feature comprising a gate dielectric layer, wherein the gate dielectric layer traverses the fin structure to overlay a central portion of the fin structure and opposite side portions of the fin structure that are located in respective undercuts formed in respective portions of a dielectric layer located adjacent to opposite sidewalls of the gate feature, wherein the undercuts extend beyond respective sidewalls of the gate feature and away from the central portion of the fin structure.

A semiconductor device includes a semiconductor substrate, a plurality of semiconductor fins, a gate stack and an epitaxy structure. The semiconductor fins are present on the semiconductor substrate. The semiconductor fins respectively include recesses therein. The gate stack is present on portions of the semiconductor fins that are adjacent to the recesses. The epitaxy structure is present across the recesses of the semiconductor fins. The epitaxy structure includes a plurality of corners and at least one groove present between the corners, and the groove has a curvature radius greater than that of at least one of the corners.

A semiconductor device includes: an active fin disposed on a substrate; a gate structure overlapping the active fin; source/drain regions disposed on both sides of the gate structure and on the active fin; and contact structures respectively connected to the source/drain regions, wherein the gate structure includes: a pair of gate spacers spaced apart from each other to provide a trench; a first gate electrode disposed in the trench and extending along an upper surface and a lateral surface of the active fin; a second gate electrode disposed on the first gate electrode in the trench, wherein the first gate electrode is not disposed between the second gate electrode and the pair of gate spacers; and a gate insulating film disposed between the pair of gate spacers and interposed between the first gate electrode and the active fin.

The disclosed subject matter provides a semiconductor structure and fabrication method thereof. In a semiconductor structure, a dielectric layer, a plurality of discrete gate structures, and a plurality of sidewall spacers are formed on a semiconductor substrate. The plurality of discrete gate structures and sidewall spacers are formed in the dielectric layer, and a sidewall spacer is formed on each side of each gate structure. A top portion of each gate structure and a top portion of the dielectric layer between neighboring sidewall spacers of neighboring gate structures are removed. A protective layer is formed on each of the remaining dielectric layer and the remaining gate structures. Contact holes are formed on the semiconductor substrate, between neighboring sidewall spacers, and on opposite sides of the protective layer on the remaining dielectric layer. A metal plug is formed in each contact hole.

A semiconductor device with reinforced gate spacers and a method of fabricating the same. The semiconductor device includes low-k dielectric gate spacers adjacent to a gate structure. A high-k dielectric material is disposed over an upper surface of the low-k dielectric gate spacers to prevent unnecessary contact between the gate structure and a self-aligned contact structure. The high-k dielectric material may be disposed, if desired, over an upper surface of the gate structure to provide additional isolation of the gate structure from the self-aligned contact structure.

A varactor transistor includes a semiconductor fin having a first conductivity type, a plurality of gate structures separated from each other and surrounding a portion of the semiconductor fin. The plurality of gates structures include a dummy gate structure on an edge of the semiconductor fin, and a first gate structure spaced apart from the dummy gate structure. The dummy gate structure and the gate structure each include a gate insulator layer on a surface portion of the semiconductor fin, a gate on the gate insulator layer, and a spacer on the gate. The varactor transistor also includes a raised source/drain region on the semiconductor fin and between the dummy gate structure and the first gate structure, the raised source/drain region and the gate of the dummy gate structure being electrically connected to a same potential.