Inner spacers between a source/drain region of a nanostructure transistor and sacrificial nanostructure layers of the nanostructure transistor are removed prior to formation of a gate structure of the nanostructure transistor. The sacrificial nanostructure layers are removed, and then the inner spacers are removed. The sacrificial nanostructure layers are then replaced with the gate structure of the nanostructure transistor such that the gate structure and the source/drain region are spaced apart by air gaps that result from the removal of the inner spacers. The dielectric constant (or relative permittivity) of the air gaps between the source/drain region and the gate structure is less than the dielectric constant of the material of the inner spacers. The lesser dielectric constant of the air gaps reduces the amount of capacitance between the source/drain region and the gate structure.

A method includes forming a first and a second gate dielectric on a first semiconductor channel region and a second semiconductor channel region overlapping the first semiconductor region, forming a first dipole film on the first gate dielectric, wherein the first dipole film comprises a first dipole dopant of a first type, and forming a second dipole film on the second gate dielectric. A drive-in process is performed to drive dipole dopants in the first dipole film and the second dipole film into the first gate dielectric and the second gate dielectric, respectively. The first dipole film and the second dipole film are removed. A gate electrode is formed on both of the first gate dielectric and the second gate dielectric to form a first transistor and a second transistor.

A method includes forming a lower semiconductor region, forming an upper semiconductor region overlapping the lower semiconductor region, forming a lower gate dielectric and an upper gate dielectric on the lower semiconductor region and the upper semiconductor region, respectively, forming a lower gate electrode on the lower gate dielectric and the upper gate dielectric, etching back the lower gate electrode, forming a gate isolation layer on the lower gate electrode that has been etched back, and forming an upper gate electrode over the gate isolation layer. The upper gate electrode is on the upper gate dielectric.

A method includes forming a first bottom-tier transistor; forming a second bottom-tier transistor, the first and second bottom-tier transistors sharing a same source/drain region; forming a first top-tier transistor over the first bottom-tier transistor, the first top-tier transistor comprising a first channel layer and a first gate structure around the first channel layer; forming a second top-tier transistor over the second bottom-tier transistor, the second top-tier transistor comprising a second channel layer and a second gate structure around the second channel layer, the first and second top-tier transistors sharing a same source/drain region, wherein from a top view, a first dimension of the first channel layer in a lengthwise direction of the first gate structure is different than a second dimension of the second channel layer in the lengthwise direction of the first gate structure.

Integrated circuit structures having differential epitaxial source or drain dent are described. For example, an integrated circuit structure includes a first sub-fin structure beneath a first stack of nanowires or fin. A second sub-fin structure is beneath a second stack of nanowires or fin. A first epitaxial source or drain structure is at an end of the first stack of nanowires of fin, the first epitaxial source or drain structure having no dent or a shallower dent therein. A second epitaxial source or drain structure is at an end of the second stack of nanowires or fin, the second epitaxial source or drain structure having a deeper dent therein.

A semiconductor device that has two transistors and a source/drain contact. The first transistor has a layer of semiconductor material that acts as a channel, a structure that serves as a gate and wraps around the semiconductor channel layer, and two epitaxy structures on either end of the semiconductor channel layer that function as the source and drain. The second transistor is situated above the first transistor and has similar components, including a semiconductor channel layer, gate structure, and source/drain epitaxy structures. The connection between the first and second source/drain epitaxy structures is made by a source/drain contact that passes through one of the second source/drain epitaxy structures. This contact is made up of a metal plug and a metal liner that lines the plug.

A method of forming a complementary field-effect transistor (CFET) device includes: forming a plurality of channel regions stacked vertically over a fin; forming an isolation structure between a first subset of the plurality of channel regions and a second subset of the plurality of channel regions; forming a gate dielectric material around the plurality of channel regions and the isolation structure; forming a work function material around the gate dielectric material; forming a silicon-containing passivation layer around the work function material; after forming the silicon-containing passivation layer, removing a first portion of the silicon-containing passivation layer disposed around the first subset of the plurality of channel regions and keeping a second portion of the silicon-containing passivation layer disposed around the second subset of the plurality of channel regions; and after removing the first portion of the silicon-containing passivation layer, forming a gate fill material around the plurality of channel regions.

Method to form low-contact-resistance contacts to source/drain features is provided. A method of the present disclosure includes receiving a workpiece including an opening that exposes a surface of an n-type source/drain feature and a surface of a p-type source/drain feature, lateral epitaxial structures etching on the n-type source/drain feature creating the offset from the sidewall of the dielectric layer, depositing a silicide layer and the offset between etched epitaxial structures and sidewall of the dielectric layer is eliminated. The lateral epitaxial structures etching includes a reactive-ion etching (RIE) process and an atomic layer etching (ALE) process.

A method includes forming a fin structure including first and second sacrificial layers and first and second channel layers over a substrate; forming a dummy gate structure across the fin structure; forming gate spacers on opposite sides of the dummy gate structure; forming first source/drain epitaxial layers on opposite sides of the first channel layer; forming second source/drain epitaxial layers on opposite sides of the second channel layer; removing the dummy gate structure and the first and second sacrificial layers to form a gate trench defined by the gate spacers; forming an oxynitride layer in the gate trench to surround the first channel layer; forming a dipole layer to surround the oxynitride layer; performing an anneal process to drive dipole dopants into the oxynitride layer; and depositing a high-k gate dielectric layer and a work function metal layer in the gate trench to form a gate structure.

A material stack comprising a plurality of bi-layers, each bi-layer comprising two semiconductor material layers, is fabricated into a transistor structure including a first stack of channel materials that is coupled to an n-type source and drain and in a vertical stack with a second stack of channel materials that is coupled to a p-type source drain. Within the first stack of channel material layers a first of two semiconductor material layers may be replaced with a first gate stack while within the second stack of channel materials a second of two semiconductor material layers may be replaced with a second gate stack.