A semiconductor device includes; an active pattern on a substrate, a source/drain pattern on the active pattern, a channel pattern connected to the source/drain pattern and including semiconductor patterns spaced apart in a vertical stack, and a gate electrode extending across the channel pattern. The semiconductor patterns includes a first semiconductor pattern and a second semiconductor pattern. The gate electrode includes a first part between the substrate and the first semiconductor pattern and a second part between the first semiconductor pattern and the second semiconductor pattern. A width of the first part varies with a depth of the first part, such that a width of a middle portion of the first part is less than a width of a lower portion of the first part and a width of an upper portion of the first part.

A method comprises forming a first fin including alternating first channel layers and first sacrificial layers and a second fin including alternating second channel layers and second sacrificial layers, forming a capping layer over the first and the second fin, forming a dummy gate stack over the capping layer, forming source/drain (S/D) features in the first and the second fin, removing the dummy gate stack to form a gate trench, removing the first sacrificial layers and the capping layer over the first fin to form first gaps, removing the capping layer over the second fin and portions of the second sacrificial layers to from second gaps, where remaining portions of the second sacrificial layers and the capping layers form a threshold voltage (V.sub.t) modulation layer, and forming a metal gate stack in the gate trench, the first gaps, and the second gaps.

A semiconductor device may include a substrate including first and second active regions and a field region therebetween, first and second active patterns respectively provided on the first and second active regions, first and second source/drain patterns respectively provided on the first and second active patterns, a first channel pattern between the first source/drain patterns and a second channel pattern between the second source/drain patterns, and a gate electrode extended from the first channel pattern to the second channel pattern to cross the field region. Each of the first and second channel patterns may include semiconductor patterns, which are stacked to be spaced apart from each other. A width of a lower portion of the gate electrode on the field region may decrease with decreasing distance from a top surface of the substrate.

A semiconductor structure includes a first field effect transistor including a first gate spacer having first laterally-straight bottom edges that coincide with top edges of first laterally-straight sidewalls of the first gate dielectric. The semiconductor structure further includes a second field effect transistor including a second gate dielectric that includes at least one discrete gate-dielectric opening that overlies a respective second active region, and a second gate spacer including a contoured portion that overlies and laterally surrounds a second gate electrode, and at least one horizontally-extending portion that overlies the second active region and including at least one discrete gate-spacer openings. The second field effect transistor may have a symmetric or non-symmetric configuration.

A semiconductor fabrication method includes: forming an epitaxial stack including at least one sacrificial epitaxial layer and at least one channel epitaxial layer; forming a plurality of fins in the epitaxial stack; performing tuning operations to prevent a width of the sacrificial epitaxial layer expanding beyond a width of the channel epitaxial layer during operations to form isolation features; forming the isolation features between the plurality of fins, wherein the width of the sacrificial epitaxial layer does not expand beyond the width of the channel epitaxial layer; forming a sacrificial gate stack; forming gate sidewall spacers on sidewalls of the sacrificial gate stack; forming inner spacers around the sacrificial epitaxial layer and the channel epitaxial layer; forming source/drain features; removing the sacrificial gate stack and sacrificial epitaxial layer; and forming a replacement metal gate, wherein the metal gate is shielded from the source/drain features.

A non-volatile memory cell includes a p-channel non-volatile transistor having a source and a drain defining a channel and a gate overlying the channel and an n-channel non-volatile transistor having a source and a drain defining a channel and a gate overlying the channel. In at least one of the p-channel non-volatile transistor and the n-channel non-volatile transistor, a lightly-doped drain region extends from the drain into the channel.

A method of forming a gate structure for a semiconductor device that includes forming first spacers on the sidewalls of replacement gate structures that are present on a fin structure, wherein an upper surface of the first spacers is offset from an upper surface of the replacement gate structure, and forming at least second spacers on the first spacers and the exposed surfaces of the replacement gate structure. The method may further include substituting the replacement gate structure with a functional gate structure having a first width portion in a first space between adjacent first spacers, and a second width portion having a second width in a second space between adjacent second spacers, wherein the second width is greater than the first width.

Semiconductor devices with airgap spacers and methods of forming the same include forming a lower spacer that defines a gate region. A sacrificial upper spacer is formed directly above the lower spacer. A gate stack is formed in the gate region. The sacrificial upper spacer is etched away to form an upper spacer opening. An airgap spacer is formed in the upper spacer opening. The airgap spacer includes a dielectric material that encapsulates an internal void.

An integrated circuit die includes a silicon substrate. PMOS and NMOS transistors are formed on the silicon substrate. The carrier mobilities of the PMOS and NMOS transistors are increased by introducing tensile stress into the channel regions of the NMOS transistors and compressive stress into the channel regions of the PMOS transistors. Tensile stress is introduced by including a region of SiGe below the channel region of the NMOS transistors. Compressive stress is introduced by including regions of SiGe in the source and drain regions of the PMOS transistors.

A semiconductor device includes first and second gate structures on a substrate respectively corresponding to an n-type and a p-type transistor, a first source/drain on the substrate corresponding to the n-type transistor, a second source/drain on the substrate corresponding to the p-type transistor, a first contact trench over the first source/drain and adjacent the first gate structure, a second contact trench over the second source/drain and adjacent the second gate structure, a first liner layer in the first trench positioned at a bottom part of the first trench, a second liner layer in the second trench and on the first liner layer in the first trench, a metallization layer in the first and second trenches on the second liner layer, and a first silicide contact between the first liner layer and the first source/drain and a second silicide contact between the second liner layer and the second source/drain.