The disclosure relates to semiconductor structures and, more particularly, to one or more devices with an engineered layer for modulating voltage threshold (Vt) and methods of manufacture. The method includes finding correlation of thickness of a buffer layer to out-diffusion of dopant into extension regions during annealing of a doped layer formed on the buffer layer. The method further includes determining a predetermined thickness of the buffer layer to adjust device performance characteristics based on the correlation of thickness of the buffer layer to the out-diffusion. The method further includes forming the buffer layer adjacent to gate structures to the predetermined thickness.

A semiconductor device includes a semiconductor substrate and a control electrode provided on a first surface side of the semiconductor substrate. The semiconductor substrate includes a first area on the first surface side and two second areas on the first surface side of the first area. The two second areas are arranged along the first surface. The control electrode provided above a portion of the first area between the two second areas. The first area includes a main portion and a peripheral edge portion extending outward from the main portion along the first surface. A depth of the peripheral edge portion from the first surface is shallower than a depth of the main portion from the first surface; and the peripheral edge portion has a concentration of second conductivity type impurities lower than a concentration of the second conductivity type impurities at a surface of the main portion.

Methods and apparatus for quantum point contacts. In an arrangement, a quantum point contact device includes at least one well region in a portion of a semiconductor substrate and doped to a first conductivity type; a gate structure disposed on a surface of the semiconductor substrate; the gate structure further comprising a quantum point contact formed in a constricted area, the constricted area having a width and a length arranged so that a maximum dimension is less than a predetermined distance equal to about 35 nanometers; a drain/source region in the well region doped to a second conductivity type opposite the first conductivity type; a source/drain region in the well region doped to the second conductivity type; a first and second lightly doped drain region in the at least one well region. Additional methods and apparatus are disclosed.

An integrated circuit may be formed by forming a sacrificial silicon nitride feature. At least a portion of the sacrificial silicon nitride feature may be removed by placing the integrated circuit in a two-step oxidized layer etch tool and removing a surface layer of oxidized silicon from the sacrificial silicon nitride feature using a two-step etch process. The two-step etch process exposes the integrated circuits to reactants from a plasma source at a temperature less than 40 C. and subsequently heating the integrated circuit to 80 C. to 120 C. while in the two-step oxidized layer etch tool. While the integrated circuit is in the two-step oxidized layer etch tool, without exposing the integrated circuit to an ambient containing more than 1 torr of oxygen, at least a portion of the sacrificial silicon nitride feature is removed using fluorine-containing etch reagents, substantially free of ammonia.

A method of controlling the facet height of raised source/drain epi structures using multiple spacers, and the resulting device are provided. Embodiments include providing a gate structure on a SOI layer; forming a first pair of spacers on the SOI layer adjacent to and on opposite sides of the gate structure; forming a second pair of spacers on an upper surface of the first pair of spacers adjacent to and on the opposite sides of the gate structure; and forming a pair of faceted raised source/drain structures on the SOI, each of the faceted source/drain structures faceted at the upper surface of the first pair of spacers, wherein the second pair of spacers is more selective to epitaxial growth than the first pair of spacers.

Forming a semiconductor structure includes forming a dummy gate stack on a substrate including a sacrificial spacer on the peripheral of the dummy gate stack. The dummy gate stack is partially recessed. The sacrificial spacer is etched down to the partially recessed dummy gate stack. Remaining portions of the sacrificial spacer are etched leaving gaps on sides of a remaining portion of the dummy gate stack. A first low-k spacer portion and a second low-k spacer portion are formed to fill gaps around the remaining portions of the dummy gate stack and extending vertically along a sidewall of a dummy gate cavity. The first and second low-k spacer portions are etched. A poly pull process is performed on the remaining portions of the dummy gate stack. A replacement metal gate (RMG) structure is formed with the first low-k spacer portion and the second low-k spacer portion.

A semiconductor structure including a semiconductor material portion located on a substrate and extending along a lengthwise direction, a gate stack overlying a portion of the semiconductor material portion, and a first low-k spacer portion and a second low-k spacer portion abutting the gate stack and spaced from each other by the gate stack along said lengthwise direction. The first low-k spacer portion and the second low-k spacer portion each part of a recessed dummy gate structure on the substrate and a sacrificial spacer with gaps around and above a portion of the dummy gate stack. The gaps are filled in with the first low-k spacer portion and the second low-k spacer portion.

Semiconductor devices include a semiconductor substrate containing a source region and a drain region, a gate structure supported by the semiconductor substrate between the source region and the drain region, a composite drift region in the semiconductor substrate, the composite drift region extending laterally from the drain region to at least an edge of the gate structure, the composite drift region including dopant having a first conductivity type, wherein at least a portion of the dopant is buried beneath the drain region at a depth exceeding an ion implantation range, and a well region in the semiconductor substrate. The well region has a second conductivity type and is configured to form a channel therein under the gate structure during operation. Methods for the fabrication of semiconductor devices are described.

A semiconductor device includes device isolation layer on a substrate to define an active region, a first gate electrode on the active region extending in a first direction parallel to a top surface of the substrate, a second gate electrode on the device isolation layer and spaced apart from the first gate electrode in the first direction, a gate spacer between the first gate electrode and the second gate electrode, and source/drain regions in the active region at opposite sides of the first gate electrode. The source/drain regions are spaced apart from each other in a second direction that is parallel to the top surface of the substrate and crossing the first direction, and, when viewed in a plan view, the first gate electrode is spaced apart from a boundary between the active region and the device isolation layer.

A semiconductor device having n-type field-effect-transistor (NFET) structure and a method of fabricating the same are provided. The NFET structure of the semiconductor device includes a silicon substrate, at least one source/drain portion and a cap layer. The source/drain portion can be disposed within the silicon substrate, and the source/drain portion comprises at least one n-type dopant-containing portion. The cap layer overlies and covers the source/drain portion, and the cap layer includes silicon carbide (SiC) or silicon germanium (SiGe) with relatively low germanium concentration, thereby preventing n-type dopants in the at least one n-type dopant-containing portion of the source/drain portion from being degraded after sequent thermal and cleaning processes.