A semiconductor device and methods of fabricating the same are disclosed. The method includes forming a fin structure on a substrate, forming a superlattice structure with first and second nanostructured layers on the fin structure, forming a polysilicon structure around the superlattice structure, forming a source/drain opening within the superlattice structure, forming a first conductivity type S/D region within a first portion of the S/D opening, forming an isolation layer on the first conductivity type S/D region and within a second portion of the S/D opening, forming a second conductivity type S/D region on the isolation layer and within a third portion the S/D opening, and replacing the polysilicon structure and the second nanostructured layers with a gate structure that surrounds the first nanostructured layers. Materials of the first and second nanostructured layers are different from each other and the second conductivity type is different from the first conductivity type.

A device includes first nanostructures over a substrate; second nanostructures over the substrate, wherein the first nanostructures are laterally separated from the second nanostructures by an isolation structure between the first nanostructures and the second nanostructures; a first gate structure around each first nanostructure and around each second nanostructure, wherein the first gate structure extends over the isolation structure; third nanostructures over the substrate; and a second gate structure around each third nanostructure, wherein the second gate structure is separated from the first gate structure by a dielectric wall.

A method for fabricating semiconductor devices is disclosed. The method includes forming a first fin structure and a second fin structure in a first region and a second region of a substrate, respectively, wherein the first and second fin structure and the substrate comprise a first semiconductor material; forming a first liner structure and a second liner structure at least extending along sidewalls of the first fin structure and sidewalls of the second fin structure, respectively; replacing an upper portion of the second fin structure with a second semiconductor material, while leaving the first fin structure substantially intact; and exposing a top surface and upper sidewalls of the first fin structure, and a top surface and upper sidewalls of the second fin structure.

A method for forming a semiconductor device structure is provided. The method includes providing a substrate having a base, a first fin, and a second fin over the base. The method includes forming a gate stack over the first fin and the second fin. The method includes forming a first spacer over gate sidewalls of the gate stack and a second spacer adjacent to the second fin. The method includes partially removing the first fin and the second fin. The method includes forming a first source/drain structure and a second source/drain structure in the first trench and the second trench respectively. A first ratio of a first height of the first merged portion to a second height of a first top surface of the first source/drain structure is greater than or equal to about 0.5.

A semiconductor device includes a drain, a source, a gate electrode, and a nanowire between the source and drain. The nanowire has a first section with a first thickness and a second section with a second thickness greater than the first thickness. The second section is between the first section and at least one of the source or drain. The first nanowire includes a channel when a voltage is applied to the gate electrode.

A structure has stacks of semiconductor layers over a substrate and adjacent a dielectric feature. A gate dielectric is formed wrapping around each layer and the dielectric feature. A first layer of first gate electrode material is deposited over the gate dielectric and the dielectric feature. The first layer on the dielectric feature is recessed to a first height below a top surface of the dielectric feature. A second layer of the first gate electrode material is deposited over the first layer. The first gate electrode material in a first region of the substrate is removed to expose a portion of the gate dielectric in the first region, while the first gate electrode material in a second region of the substrate is preserved. A second gate electrode material is deposited over the exposed portion of the gate dielectric and over a remaining portion of the first gate electrode material.

Methods are disclosed for forming fins in transistors. In one embodiment, a method of fabricating a device includes forming silicon fins on a substrate and forming a dielectric layer on the substrate and adjacent to the silicon fins such that an upper region of each silicon fin is exposed. Germanium may then be epitaxially grown germanium on the upper regions of the silicon fins to form germanium fins.

A semiconductor device includes a plurality of first nanosheets of a first conductive type, a plurality of second nanosheets of a second conductive type and a gate structure. The gate structure wraps the first nanosheets and the second nanosheets, wherein a first thickness of at least one of the first nanosheets is smaller than a second thickness of at least one of the second nanosheets.

In an embodiment, a method includes: patterning a lower semiconductor nanostructure, an upper semiconductor nanostructure, and a dummy nanostructure, the dummy nanostructure disposed between the lower semiconductor nanostructure and the upper semiconductor nanostructure, the dummy nanostructure including doped silicon; forming an opening between the lower semiconductor nanostructure and the upper semiconductor nanostructure by etching the doped silicon of the dummy nanostructure; forming an isolation structure in the opening; and depositing a gate dielectric around the isolation structure, the upper semiconductor nanostructure, and the lower semiconductor nanostructure.

A method for forming a semiconductor device structure is provided. The method includes forming a first fin structure and a second fin structure. Each of the first fin structure and the second fin structure has multiple sacrificial layers and multiple semiconductor layers laid out in an alternating manner, and the first fin structure is substantially as wide as the second fin structure. The method also includes forming a gate stack wrapped around the first fin structure and the second fin structure. The method further includes simultaneously removing the sacrificial layers of the first fin structure and the second fin structure. Remaining portions of the semiconductor layers of the first fin structure form multiple first semiconductor nanostructures, and remaining portions of the semiconductor layers of the second fin structure form multiple second semiconductor nanostructures. Each of the first semiconductor nanostructures is thicker than each of the second semiconductor nanostructures.