In a method, a gate structure is formed over a substrate, and source/drain (S/D) features are formed in the substrate and interposed by the gate structure. At least one of the S/D features is formed by forming a first semiconductor material including physically discontinuous portions, forming a second semiconductor material over the first semiconductor material, and forming a third semiconductor material over the second semiconductor material. The second semiconductor material has a composition different from a composition of the first semiconductor material. The third semiconductor material has a composition different from the composition of the second semiconductor material.

A semiconductor device includes a semiconductor substrate, a trench, and a gate structure. The trench is disposed in the semiconductor substrate. The gate structure is disposed on the semiconductor substrate. The gate structure includes a gate electrode, a first gate oxide layer, and a second gate oxide layer. A first portion of the gate electrode is disposed in the trench, and a second portion of the gate electrode is disposed outside the trench. The first gate oxide layer is disposed between the gate electrode and the semiconductor substrate. At least a portion of the first gate oxide layer is disposed in the trench. The second gate oxide layer is disposed between the second portion of the gate electrode and the semiconductor substrate in a vertical direction. A thickness of the second gate oxide layer is greater than a thickness of the first gate oxide layer.

In an embodiment, a device includes: a fin on a substrate, fin having a Si portion proximate the substrate and a SiGe portion distal the substrate; a gate stack over a channel region of the fin; a source/drain region adjacent the gate stack; a first doped region in the SiGe portion of the fin, the first doped region disposed between the channel region and the source/drain region, the first doped region having a uniform concentration of a dopant; and a second doped region in the SiGe portion of the fin, the second doped region disposed under the source/drain region, the second doped region having a graded concentration of the dopant decreasing in a direction extending from a top of the fin to a bottom of the fin.

Some embodiments of the present disclosure provide a semiconductor structure, including a substrate and a regrowth region. The substrate is made of a first material with a first lattice constant, and the regrowth region is made of the first material and a second material, having a lattice constant different from the first lattice constant. The regrowth region is partially positioned in the substrate. The regrowth region has a “tip depth” measured vertically from a surface of the substrate to a widest vertex of the regrowth region, and the tip depth being less than 10 nm. The regrowth region further includes a top layer substantially made of the first material, and the top layer has substantially the first lattice constant.

A semiconductor structure and a method for forming a semiconductor structure are provided. The semiconductor structure includes a substrate; a gate electrode disposed within the substrate; a gate dielectric layer disposed within the substrate and surrounding the gate electrode; a plurality of first protection structures disposed over the gate electrode; a second protection structure disposed over the gate dielectric layer; and a pair of source/drain regions on opposing sides of the gate dielectric layer.

A semiconductor device having tipless epitaxial source/drain regions and a method for its formation are described. In an embodiment, the semiconductor device comprises a gate stack on a substrate. The gate stack is comprised of a gate electrode above a gate dielectric layer and is above a channel region in the substrate. The semiconductor device also comprises a pair of source/drain regions in the substrate on either side of the channel region. The pair of source/drain regions is in direct contact with the gate dielectric layer and the lattice constant of the pair of source/drain regions is different than the lattice constant of the channel region. In one embodiment, the semiconductor device is formed by using a dielectric gate stack placeholder.

A semiconductor device and a method of manufacturing a semiconductor device are provided. The semiconductor device includes a substrate having a surface. The surface has a first portion and a second portion protruding from the first portion. The semiconductor device also includes a dielectric layer disposed on the second portion and a gate conductive layer disposed on the dielectric layer.

The present application discloses a semiconductor device and a method for fabricating the semiconductor device. The semiconductor device includes a substrate, a gate structure positioned on the substrate, and a plurality of word lines positioned apart from the gate structure, wherein a top surface of the gate structure and top surfaces of the plurality of word lines are at a same vertical level.

A semiconductor device having tipless epitaxial source/drain regions and a method for its formation are described. In an embodiment, the semiconductor device comprises a gate stack on a substrate. The gate stack is comprised of a gate electrode above a gate dielectric layer and is above a channel region in the substrate. The semiconductor device also comprises a pair of source/drain regions in the substrate on either side of the channel region. The pair of source/drain regions is in direct contact with the gate dielectric layer and the lattice constant of the pair of source/drain regions is different than the lattice constant of the channel region. In one embodiment, the semiconductor device is formed by using a dielectric gate stack placeholder.

A semiconductor device includes a plurality of gate electrodes over a substrate, and a source/drain epitaxial layer. The source/drain epitaxial layer is disposed in the substrate and between two adjacent gate electrodes, wherein a bottom surface of the source/drain epitaxial layer is buried in the substrate to a depth less than or equal to two-thirds of a spacing between the two adjacent gate electrodes.