Semiconductor device and methods of formation

Abstract

Some embodiments described herein provide nanostructured transistors and methods for forming the same. The nanostructured transistor includes concave regions at the ends of a plurality of channel layers. The nanostructured transistor further includes convex portions of epitaxial material, which are part of the source / drain regions of the nanostructured transistor and extend into the concave regions. Masking, etching, and cleaning operations performed after the deposition of a buffer layer can form the concave regions.

Description

Semiconductor devices and methods for forming the same The present invention relates to a semiconductor device and a method of forming the same, and particularly to an improved semiconductor device and a method of forming the same. As semiconductor device manufacturing advances and technology node sizes shrink, transistors can be affected by short-channel effects (SCEs), such as hot carrier degradation, barrier lowering, and quantum confinement (among other examples). Furthermore, as the gate length of transistors used in smaller technology nodes decreases, source / drain (S / D) electron tunneling increases, which in turn increases the off-current (the current flowing through the transistor's channels when it is in off configuration). Silicon (Si) / silicon germanium (SiGe) nanostructure transistors, such as nanowires, nanosheets, and gate-all-around (GAA) devices, are potential candidates for overcoming short-channel effects at smaller technology nodes. Compared to other types of transistors, nanostructured transistors are an efficient structure that can reduce SCE and improve carrier mobility. One embodiment provides a semiconductor device. The semiconductor device includes a plurality of channel layers above a semiconductor substrate, wherein the plurality of channel layers are arranged in a direction perpendicular to the semiconductor substrate, and wherein the plurality of channel layers include concave regions at the ends of the plurality of channel layers. The semiconductor device includes a gate structure surrounding each of the plurality of channel layers. The semiconductor device includes source / drain regions adjacent to the plurality of channel layers and the gate structure. Another embodiment provides a method for forming a semiconductor device. The method includes forming a plurality of nanostructure layers over a semiconductor substrate in a direction perpendicular to the semiconductor substrate, wherein the plurality of nanostructure layers include a plurality of sacrificial layers alternating with a plurality of channel layers. The method includes forming inner spacers at the ends of the plurality of sacrificial layers. The method includes forming concave regions at the ends of the plurality of channel layers. The method includes forming source / drain regions adjacent to the inner spacers and concave regions, wherein forming the source / drain regions includes a convex portion of the epitaxial layer forming the source / drain regions within the concave regions at the ends of the plurality of channel layers. The method includes forming a gate structure, and the gate structure includes surrounding a portion of the plurality of channel layers. Another embodiment provides a method for forming a semiconductor device. The method includes forming a first plurality of channel layers for an n-type metal-oxide-semiconductor nanostructure transistor and a second plurality of channel layers for a p-type metal-oxide-semiconductor nanostructure transistor over a semiconductor substrate. Forming the first plurality of channel layers includes forming the first plurality of channel layers along a first axis perpendicular to the semiconductor substrate, and forming the second plurality of channel layers includes forming the second plurality of channel layers along a second axis perpendicular to the semiconductor substrate. The method includes depositing a masking material over the ends of the first plurality of channel layers. The method includes removing a portion from the ends of the second plurality of channel layers to form a concave region at the ends of the second plurality of channel layers. The method includes removing the masking material after forming the concave region. The formation method includes forming a first source / drain region adjacent to a first plurality of channel layers and a second source / drain region adjacent to a second plurality of channel layers, wherein forming the first source / drain region includes forming a first portion of an epitaxial layer above the ends of the first plurality of channel layers, and wherein forming the second source / drain region includes forming a second portion of an epitaxial layer in a concave region at the ends of the second plurality of channel layers. The formation method also includes forming a first gate structure and a second gate structure, wherein forming the first gate structure includes forming a portion surrounding the first plurality of channel layers, and wherein forming the second gate structure includes forming a portion surrounding the second plurality of channel layers. The following disclosure provides numerous different embodiments or examples for implementing various components of the provided subject matter. Specific examples of components and arrangements are described below to simplify this disclosure. Of course, these specific examples are merely illustrative and not intended to be limiting. For instance, if this disclosure describes a first component formed over or on a second component, it may include embodiments where the first and second components are formed in direct contact, and may also include embodiments where other components are formed between the first and second components, so that the first and second components may not be in direct contact. Furthermore, element symbols and / or characters may be repeated in various examples in this disclosure. Such repetition itself does not limit the relationship between the various embodiments and / or configurations discussed, but is for simplification and clarity. Furthermore, for ease of description, this document may use spatially related terms such as "beneath," "below," "lower," "above," "upper," and similar terms to describe the relationship between one element or component and another element(s) shown in the diagrams. In addition to the directions depicted in the diagrams, the spatially related terms are intended to cover different orientations of the device in use or operation. The device may be oriented in other directions (rotated 90 degrees or otherwise), and the spatially related terms used herein may be interpreted accordingly. In some cases, reducing the geometry and size characteristics of a fin field-effect transistor (FINFET) can degrade its performance. For example, as the process node of FINFET technology decreases, the likelihood of short-channel effects, such as a reduction in the drain-induced barrier, may increase. Furthermore, as the gate length of a FINFET decreases, the potential for electron tunneling and leakage current increases. Nanostructured transistors (e.g., nanowire transistors, nanosheet transistors, fully wound gate (GAA) transistors, multi-bridge channel transistors, nanoribbon transistors, and / or other types of nanostructured transistors) can overcome one or more of the drawbacks of finFETs mentioned above. However, nanostructured transistors face manufacturing challenges that can lead to performance problems and / or device failures. For example, increasing the length of the nanosheets used to form the channels of a nanostructured transistor may increase the channel resistance (Rch) of the nanostructured transistor, while a small amount of epitaxial material in the source / drain regions may increase the parasitic resistance (R). p Due to the irregular shape between the ends of the nanosheets and the internal spacers above or below the ends of the nanosheets, the epitaxial material in the source / drain regions may be susceptible to damage, such as non-merge issues. Some embodiments described herein provide nanostructured transistors and methods for their formation. The nanostructured transistor includes concave-shaped regions located at the ends of a plurality of channel layers. The nanostructured transistor also includes convex-shaped portions of epitaxial material, which are part of the source / drain regions of the nanostructured transistor and extend into the concave regions. Masking, etching, and cleaning operations performed after the deposition of a buffer layer can form the concave regions. This improves the performance of nanostructured transistors. For example, the channel length of a nanostructured transistor can be reduced to lower its channel resistance (Ro). ch Additionally or alternatively, the volume of epitaxial material in the source / drain regions can be increased to reduce the parasitic resistance (R0) of the nanostructured transistor. p R ch and / or R p This reduction can increase the drive current of nanostructured transistors. The concave ends of the channel layer can also reduce the likelihood of non-merging issues, thereby improving the yield of semiconductor devices including nanostructured channel transistors. Figure 1 is a diagram of an exemplary environment 100 in which the systems and / or methods described herein can be implemented. As shown in Figure 1, environment 100 may include a plurality of semiconductor process tools 102-112 and a wafer / die transport tool 114. The plurality of semiconductor process tools 102-112 may include a deposition tool 102, an exposure tool 104, a developer tool 106, an etching tool 108, a planarization tool 110, a plating tool 112, and / or other types of semiconductor process tools. The tools included in exemplary environment 100 may be found in semiconductor clean rooms, semiconductor foundries, semiconductor processing facilities, and / or manufacturing facilities, among other examples. The deposition tool 102 is a semiconductor processing tool, comprising a semiconductor processing chamber and one or more means for depositing various types of materials onto a substrate. In some embodiments, the deposition tool 102 includes a spin coating tool capable of depositing a photoresist layer on a substrate such as a wafer. In some embodiments, the deposition tool 102 includes a chemical vapor deposition (CVD) tool, such as a plasma-enhanced CVD (PECVD) tool, a high-density plasma CVD (HDP-CVD) tool, a sub-atmospheric CVD (SACVD) tool, a low-pressure CVD (LPCVD) tool, an atomic layer deposition (ALD) tool, a plasma-enhanced atomic layer deposition (PEALD) tool, or other types of CVD tools. In some embodiments, the deposition tool 102 includes a physical vapor deposition (PVD) tool, such as a sputtering tool or another type of PVD tool. In some embodiments, the deposition tool 102 includes an epitaxial tool, and the epitaxial tool is configured to form layers and / or regions of the apparatus by epitaxial growth. In some embodiments, the exemplary environment 100 includes a plurality of types of deposition tools 102. Exposure tool 104 is a semiconductor manufacturing tool that exposes a photoresist layer to a radiation source, such as an ultraviolet (UV) light source (e.g., deep UV light, extreme UV (EUV) light, and / or similar sources), an x-ray source, an electron beam (e-beam) source, and / or the like. Exposure tool 104 exposes the photoresist layer to the radiation source to transfer a pattern from a photomask to the photoresist layer. The pattern may include one or more semiconductor device layer patterns for forming one or more semiconductor devices, patterns for forming one or more structures of a semiconductor device, patterns for etching various portions of a semiconductor device, and / or similar patterns. In some embodiments, exposure tool 104 includes a scanner, a stepper, or a similar type of exposure tool. The developing tool 106 is a semiconductor processing tool capable of developing a photoresist layer already exposed to a radiation source, thereby developing a pattern transferred from the exposure tool 104 to the photoresist layer. In some embodiments, the developing tool 106 develops the pattern by removing the unexposed portions of the photoresist layer. In some embodiments, the developing tool 106 develops the pattern by removing the exposed portions of the photoresist layer. In some embodiments, the developing tool 106 develops the pattern by using a chemical developer to dissolve either the exposed or unexposed portions of the photoresist layer. Etching tool 108 is a semiconductor manufacturing tool capable of etching various types of materials on a substrate, wafer, or semiconductor device. For example, etching tool 108 may include a wet etching tool, a dry etching tool, and / or the like. In some embodiments, etching tool 108 includes a chamber filled with etchant, and a substrate is placed in the chamber for a specific period of time to remove a specific amount of one or more portions of the substrate. In some embodiments, etching tool 108 uses plasma etching or plasma-assisted etching to etch one or more portions of the substrate, which may involve using ionized gas to isotropically or directionally etch one or more portions. In some embodiments, etching tool 108 includes a plasma-based asher to remove photoresist material. Planarization tool 110 is a semiconductor manufacturing tool capable of polishing or planarizing various layers of a wafer or semiconductor device. For example, planarization tool 110 may include a chemical mechanical planarization (CMP) tool and / or another type of planarization tool for polishing or planarizing layers or surfaces of deposited or electroplated material. Planarization tool 110 may use a combination of chemical and mechanical forces (e.g., chemical etching and free abrasive polishing) to polish or planarize the surface of a semiconductor device. Planarization tool 110 may incorporate a polishing pad and a retaining ring (e.g., typically having a larger diameter than the semiconductor device) to use polishing and etching chemical slurries. The polishing pad and semiconductor device may be pressed together by a dynamic polishing head and held in place by the retaining ring. Dynamic grinding heads can rotate on different axes of rotation to remove material and even flatten any irregular topography of a semiconductor device, making the semiconductor device flat or planar. Electroplating tool 112 is a semiconductor manufacturing process tool capable of electroplating one or more metal substrates (e.g., wafers, semiconductor devices, and / or the like) or a portion thereof. For example, electroplating tool 112 may include copper electroplating apparatus, aluminum electroplating apparatus, nickel electroplating apparatus, tin electroplating apparatus, compound material or alloy (e.g., tin-silver, tin-lead, and / or the like) electroplating apparatus, and / or electroplating apparatus for one or more other types of conductive materials, metals, and / or similar materials. The wafer / die transfer tool 114 includes a mobile robot, robot arm, tram or rail car, overhead hoist transport (OHT) system, automated materially handling system (AMHS), and / or other types of devices, namely, devices configured to transfer substrates and / or semiconductor devices between semiconductor process tools 102-112; devices configured to transfer substrates and / or semiconductor devices between process cavities of the same semiconductor process tool; and / or devices configured to transfer substrates and / or semiconductor devices to and from other locations, such as wafer racks, storage rooms, and / or similar locations. In some embodiments, the wafer / die transfer tool 114 may be a programmed device configured to travel a specific path and / or operate semi-autonomously or automatically. In some embodiments, the environment 100 includes a plurality of wafer / die transfer tools 114. For example, wafer / die transfer tool 114 may be included in a cluster tool or in other types of tools that include a plurality of process cavities, and may be configured to transfer substrates and / or semiconductor devices between a plurality of process cavities, to transfer substrates and / or semiconductor devices between a process cavity and a buffer area, to transfer substrates and / or semiconductor devices between a process cavity and an interface tool such as an equipment front end module (EFEM), and / or to transfer substrates and / or semiconductor devices between a process cavity and a transport carrier (e.g., a front-opening unified pod, FOUP) and so on (among other examples). In some embodiments, the wafer / die transfer tool 114 may be included in a multi-chamber (or clustered) deposition tool 102, which may include pre-clean process chambers (e.g., for cleaning or removing oxides, oxidation, and / or other types of contaminants or byproducts from the substrate and / or semiconductor device) and multiple types of deposition process chambers (e.g., process chambers for depositing different types of materials, process chambers for performing different types of deposition operations). In these embodiments, as described herein, the wafer / die transfer tool 114 is configured to transfer the substrate and / or semiconductor device between process chambers of the deposition tool 102 without destroying or removing the vacuum (or at least partial vacuum) between the process chambers and / or between process operations in the deposition tool 102. As described in conjunction with Figures 2, 3A, 3B, 4A, 4B, 5A to 5C, 6A to 6C, 7A, 7B, 8A to 8D, 9A to 9F, 10A to 10D, 11A, 11B, and 12 to 15, and other content herein, semiconductor process tools 102-112 can perform combinations of operations to form a portion of a nanostructured transistor. As an example, one combination of operations includes forming a plurality of nanostructured layers over the semiconductor substrate in a direction perpendicular to the semiconductor substrate. In some embodiments, the plurality of nanostructured layers include a plurality of sacrificial layers alternating with a plurality of channel layers. The combination of operations includes forming inner spacers at the ends of a plurality of sacrificial layers; forming concave regions at the ends of a plurality of channel layers; and forming source / drain regions adjacent to the inner spacers and concave regions. In some embodiments, forming the source / drain regions includes a convex portion of the epitaxial layer forming the source / drain regions within the concave regions at the ends of the plurality of channel layers. The combination of operations further includes forming a gate structure comprising warps around a portion of the plurality of channel layers. Additionally or alternatively, another combination of operations includes forming a first plurality of channel layers for an n-type metal-oxide semiconductor (NMOS) nanostructure transistor and a second plurality of channel layers for a p-type metal-oxide semiconductor (PMOS) nanostructure transistor over a semiconductor substrate. In some embodiments, forming the first plurality of channel layers includes forming the first plurality of channel layers along a first axis perpendicular to the semiconductor substrate, and forming the second plurality of channel layers includes forming the second plurality of channel layers along a second axis perpendicular to the semiconductor substrate. A combination of operations includes depositing a masking material over the ends of the first plurality of channel layers; removing a portion from the ends of the second plurality of channel layers to form concave regions at the ends of the second plurality of channel layers; and removing the masking material after forming the concave regions. A combination of operations includes forming a first source / drain region adjacent to the first plurality of channel layers and a second source / drain region adjacent to the second plurality of channel layers. In some embodiments, forming a first source / drain region includes forming a first portion of an epitaxial layer above the ends of the first plurality of channel layers, and forming a second source / drain region includes forming a second portion of an epitaxial layer in a concave region at the ends of the second plurality of channel layers. A combination of operations includes forming a first gate structure and a second gate structure. In some embodiments, forming a first gate structure includes forming a portion surrounding the first plurality of channel layers, and forming a second gate structure includes forming a portion surrounding the second plurality of channel layers. The number and arrangement of devices shown in Figure 1 provide one or more examples. In practice, there may be additional devices, fewer devices, different devices, or different arrangements of devices compared to those shown in Figure 1. Furthermore, the two or more devices shown in Figure 1 can be implemented in a single device, or the single device shown in Figure 1 can be implemented as multiple distributed devices. Additionally or alternatively, a group of devices in environment 100 (e.g., one or more devices) can perform one or more functions described as being performed by another group of devices in environment 100. Figure 2 is a diagram of an exemplary semiconductor device 200 described herein. Semiconductor device 200 includes one or more transistors. The one or more transistors may include nanostructure transistors, such as nanowire transistors, nanosheet transistors, gate-all-around (GAA) transistors, multi-bridge channel transistors, nanoribbon transistors, and / or other types of nanostructure transistors. Semiconductor device 200 may include one or more additional devices, structures, and / or layers not shown in Figure 2. For example, semiconductor device 200 may include additional layers and / or dies formed on and / or beneath a portion of semiconductor device 200 as shown in Figure 2. Additionally or alternatively, semiconductor device 200 as shown in Figure 2 may form one or more additional semiconductor structures and / or semiconductor devices in the same layer of an electronic device or integrated circuit (IC) including the semiconductor device. Figures 3A, 3B, 4A, 4B, 5A to 5C, 6A to 6C, 7A, 7B, 8A to 8D, 9A to 9F, and 10A to 10D are schematic cross-sectional views of various parts of the semiconductor device 200 shown in Figure 2, and correspond to various process stages in forming the nanostructure transistors of the semiconductor device 200. Semiconductor device 200 includes a semiconductor substrate 205. Semiconductor substrate 205 includes a silicon (Si) substrate, a substrate formed of a material including silicon, a III-V compound semiconductor material substrate such as gallium arsenide (GaAs), a silicon-on-insulator (SOI) substrate, a germanium (Ge) substrate, a silicon-germanium (SiGe) substrate, a silicon carbide (SiC) substrate, or other types of semiconductor substrates. Semiconductor substrate 205 may include various layers, including conductive or insulating layers formed on the semiconductor substrate. Semiconductor substrate 205 may include compound semiconductors and / or alloy semiconductors. Semiconductor substrate 205 may include various doping configurations to satisfy one or more design parameters. For example, different doping profiles (e.g., forming n-type wells and p-type wells) may be formed on a semiconductor substrate 205 in regions designed for different device types (e.g., p-type metal-oxide-semiconductor (PMOS) nanostructure transistors and n-type metal-oxide-semiconductor (NMOS) nanostructure transistors). Suitable doping may include ion implantation and / or diffusion processes of the dopant. Furthermore, the semiconductor substrate 205 may include an epitaxial layer, may be strained to enhance performance, and / or may have other suitable reinforcing elements. The semiconductor substrate 205 may include a portion of a semiconductor wafer on which other semiconductor devices are formed. Mesa regions 210 are included on (and / or extend over) the semiconductor substrate 205. Mesa regions 210 provide structures for forming nanostructures of the semiconductor device 200 thereon, such as nanostructure channels, nanostructure gate portions wrapping around each nanostructure channel, and / or sacrificial nanostructures, etc. In some embodiments, one or more mesa regions 210 are formed in and / or form fin structures (e.g., silicon fin structures) within the semiconductor substrate 205. Mesa regions 210 may comprise the same material as and be formed from the semiconductor substrate 205. In some embodiments, mesa regions 210 are doped to form different types of nanostructure transistors, such as p-type and / or n-type nanostructure transistors. In some embodiments, platform region 210 includes silicon (Si) material or other elemental semiconductor materials such as germanium (Ge). In some embodiments, platform region 210 includes alloy semiconductor materials such as silicon germanium (SiGe), gallium arsenide phosphide (GaAsP), aluminum indium arsenide (AlInAs), aluminum gallium arsenide (AlGaAs), gallium indium arsenide (GaInAs), gallium indium phosphide (GaInP), gallium indium arsenide phosphide (GaInAsP), or combinations thereof. Platform region 210 is fabricated using suitable semiconductor manufacturing processes, such as masking, photolithography, and / or etching. As an example, a portion of semiconductor substrate 205 can be etched away to form recesses in semiconductor substrate 205 to form a fin structure. These recesses can then be filled with recessed or etched-back isolation material to form shallow trench isolation (STI) regions 215 on semiconductor substrate 205 and between the fin structures. Source / drain recesses can be formed in the fin structures, resulting in platform region 210 formed between the source / drain recesses. However, other manufacturing techniques can be used for STI region 215 and / or platform region 210. STI region 215 can electrically isolate adjacent fin structures and can provide layers on which other layers and / or structures of semiconductor device 200 are formed. STI region 215 may include a dielectric material, such as silicon oxide (SiO2). x ), silicon nitride (Si x N y Silicon oxynitride (SiON), fluoride-doped silicate glass (FSG), low dielectric constant (low-k) dielectric materials, and / or other suitable insulating materials. STI region 215 may include a multilayer structure, for example, a multilayer structure having one or more layers. Semiconductor device 200 includes a plurality of nanostructured channels 220 extending between and electrically coupled to source / drain regions 225. The nanostructured channels 220 are arranged approximately perpendicular to the semiconductor substrate 205. In other words, the nanostructured channels 220 are vertically aligned or stacked on the semiconductor substrate 205. The nanostructure channel 220 includes a silicon-based nanostructure (e.g., a nanosheet or nanowire, etc.) that functions as a semiconductor channel for a nanostructured transistor in the semiconductor device 200. In some embodiments, the nanostructure channel 220 may include silicon-germanium (SiGe) or other silicon-based materials. The source / drain region 225 includes silicon (Si) with one or more dopants, such as p-type materials (e.g., boron (B) or germanium (Ge), etc.), n-type materials (e.g., phosphorus (P) or arsenic (As), etc.), and / or other types of dopants. Accordingly, the semiconductor device 200 may include a p-type metal-oxide-semiconductor (PMOS) nanostructured transistor including a p-type source / drain region 225, an n-type metal-oxide-semiconductor (NMOS) nanostructured transistor including an n-type source / drain region 225, and / or other types of nanostructured transistors. In some embodiments, buffer region 230 is included below source / drain region 225 and between fin structures above semiconductor substrate 205. Buffer region 230 can provide isolation between source / drain region 225 and adjacent plateau region 210. Buffer region 230 may be included to reduce, minimize, and / or prevent electrons traversing into plateau region 210 (e.g., instead of traversing through nanostructure channel 220, thereby reducing leakage current) and / or buffer region 230 may be included to reduce, minimize, and / or prevent dopant from source / drain region 225 to plateau region 210 (this reduces short-channel effects). A capping layer 235 may be included over and / or on the source / drain region 225. The capping layer 235 may include silicon, silicon germanium, doped silicon, doped silicon germanium, and / or other materials. The capping layer 235 may be included to reduce dopant diffusion and protect the source / drain region 225 during semiconductor process operations of the semiconductor device 200 prior to the formation of contacts. Furthermore, the capping layer 235 may facilitate the formation of metal-semiconductor (e.g., silicide) alloys. At least a subset of the nanostructure channel 220 extends through one or more gate structures 240. The gate structure 240 may be formed from one or more metallic materials, one or more high-k materials, and / or one or more other types of materials. In some embodiments, a dummy gate structure (e.g., a polysilicon (PO) gate structure or other type of gate structure) is formed to replace (e.g., before forming gate structure 240) the gate structure 240, allowing one or more other layers and / or structures of the semiconductor device 200 to be formed prior to the formation of gate structure 240. This reduces and / or prevents damage to the gate structure 240 that would otherwise be caused by the formation of one or more layers and / or structures. A replacement gate process (RGP) is then performed to remove the dummy gate structure and replace it with the gate structure 240 (e.g., the replacement gate structure). As further shown in Figure 2, a portion of the gate structure 240 is formed between pairs of nanostructure channels 220 in an alternating vertical arrangement. In other words, as shown in Figure 2, the semiconductor device 200 includes one or more vertical stacks of alternating nanostructure channels 220 and portions of the gate structure 240. In this way, the gate structure 240 surrounds the associated nanostructure channels 220 on all sides, which increases control over the nanostructure channels 220, increases the drive current of the nanostructure transistors of the semiconductor device 200, and reduces the short channel effects (SCE) of the nanostructure transistors of the semiconductor device 200. Some source / drain regions 225 and gate structures 240 can be shared between two or more nanoscale transistors in the semiconductor device 200. In these embodiments, as illustrated in the example of Figure 2, one or more source / drain regions 225 and gate structures 240 can be connected or coupled to a plurality of nanostructure channels 220. This allows the plurality of nanostructure channels 220 to be controlled by a single gate structure 240 and a pair of source / drain regions 225. Inner spacers (InSP) 245 may be included between the source / drain regions 225 and adjacent gate structures 240. Specifically, inner spacers 245 may be included between the source / drain regions 225 and a portion of the gate structure 240 surrounding a plurality of nanostructure channels 220. Inner spacers 245 may be included at the ends of a portion of the gate structure 240 surrounding the plurality of nanostructure channels 220. The inner spacers 245 are included in cavities formed between end portions of adjacent nanostructure channels 220. The inner spacers 245 are included to reduce parasitic capacitance and protect the source / drain regions 225 from etching during nanosheet release operations to remove sacrificial nanosheets between the nanostructure channels 220. The inner spacers 245 comprise silicon nitride (Si). x N y ), silicon oxide (SiO) x Silicon oxynitride (SiON), silicon oxycarbide (SiOC), silicon carbon nitride (SiCN), silicon oxycarbonnitride (SiOCN), and / or other dielectric materials. In some embodiments, the semiconductor device 200 includes hybrid fin structures (not shown). In other examples, the hybrid fin structures may also be referred to as dummy fins, H-fins, or non-active fins, etc. The hybrid fin structures may be located between adjacent source / drain regions 225, between portions of the gate structure 240, and / or between adjacent stacks of the nanostructure channel 220, etc. The hybrid fins extend in a direction approximately perpendicular to the gate structure 240. Hybrid fin structures are configured to provide electrical isolation between two or more structures and / or components included in the semiconductor device 200. In some embodiments, hybrid fin structures are configured to provide electrical isolation between two or more stacks of nanostructure channels 220. In some embodiments, hybrid fin structures are configured to provide electrical isolation between two or more source / drain regions 225. In some embodiments, hybrid fin structures are configured to provide electrical isolation between two or more gate structures or two or more portions of a gate structure. In some embodiments, hybrid fin structures are configured to provide electrical isolation between the source / drain regions 225 and the gate structure 240. Hybrid fin structures can include multiple types of dielectric materials. Hybrid fin structures can include one or more low dielectric constant (low k) dielectric materials (e.g., silicon oxide (SiO₂)). x ) and / or silicon nitride (Si x N y (etc.) and one or more high dielectric constant (high-k) dielectric materials (e.g., hafnium oxide, HfO) x A combination of (and / or other high-k dielectric materials). The semiconductor device 200 may also include an inter-layer dielectric (ILD) layer 250 above the STI region 215. The ILD layer 250 may be referred to as an ILD0 layer. The ILD layer 250 surrounds the gate structure 240 to provide electrical isolation and / or insulation between the gate structure 240 and / or the source / drain regions 225, etc. Conductive structures such as contacts and / or interconnects may be formed through the ILD layer 250 to the source / drain regions 225 and the gate structure 240 to provide control over the source / drain regions 225 and the gate structure 240. As described in conjunction with Figures 3A, 3B, 4A, 4B, 5A to 5C, 6A to 6C, 7A, 7B, 8A to 8D, 9A to 9F, 10A to 10D, 11A, 11B, and 12 to 15, and other content herein, a semiconductor device 200 may be formed to include components corresponding to one or more portions of a nanostructured transistor. For example, the semiconductor device 200 may include a plurality of channel layers above a semiconductor substrate 205. In some embodiments, the plurality of channel layers are arranged in a direction perpendicular to the semiconductor substrate 205. In some embodiments, the plurality of channel layers include concave regions at the ends of the plurality of channel layers. Semiconductor device 200 includes a gate structure (e.g., gate structure 240) surrounding each of a plurality of channel layers and a source / drain region (e.g., source / drain region 225) adjacent to the plurality of channel layers and the gate structure. As mentioned above, Figure 2 is provided as an example. Other examples may differ from those described regarding Figure 2. Figures 3A and 3B are diagrams of an exemplary embodiment 300 of the fin formation process described herein. Exemplary embodiment 300 includes an example of forming a fin structure for a semiconductor device 200 or a portion thereof. The semiconductor device 200 may include one or more additional devices, structures, and / or layers not shown in Figures 3A and 3B. The semiconductor device 200 may include additional layers and / or dies formed on layers above and / or below a portion of the semiconductor device 200 shown in Figures 3A and 3B. Additionally or alternatively, one or more additional semiconductor structures and / or semiconductor devices may be formed in the same layer of the electronic device including the semiconductor device 200. Figure 3A shows a perspective view of the semiconductor device 200 and a cross-sectional view along line segment AA in the perspective view. As shown in Figure 3A, the semiconductor device 200 is fabricated in conjunction with a semiconductor substrate 205. A stacked layer 305 is formed on the semiconductor substrate 205. The stacked layer 305 may be referred to as a superlattice. In some embodiments, one or more operations are performed in conjunction with the semiconductor substrate 205 prior to the formation of the stacked layer 305. For example, an anti-punch-through (APT) implantation operation may be performed. An APT implantation operation may be performed in one or more regions of the semiconductor substrate 205, and nanostructure channels 220 will be formed over said one or more regions. For example, the APT implantation operation is performed to reduce and / or prevent punch-through or unwanted diffusion into the semiconductor substrate 205. The stack 305 includes a plurality of alternating layers arranged in a direction approximately perpendicular to the semiconductor substrate 205. For example, the stack 305 includes vertically alternating layers of a first layer 310 and a second layer 315 on the semiconductor substrate 205. The quantity of the first layer 310 and the second layer 315 shown in Figure 3A are exemplary, and other quantities of the first layer 310 and the second layer 315 are within the scope of this disclosure. In some embodiments, the first layer 310 and the second layer 315 are formed to have different thicknesses. For example, the second layer 315 may be formed to have a greater thickness than the first layer 310. In some embodiments, the first layer 310 (or a subset thereof) is formed to have a thickness in the range of approximately 4 nanometers to approximately 7 nanometers. In some embodiments, the second layer 315 (or a subset thereof) is formed to have a thickness in the range of approximately 8 nanometers to approximately 12 nanometers. However, other values ​​for the thickness of the first layer 310 and the second layer 315 are within the scope of this disclosure. The first layer 310 includes a first material composition, and the second layer 315 includes a second material composition. In some embodiments, the first and second material compositions are the same material composition. In some embodiments, the first and second material compositions are different material compositions. As an example, the first layer 310 may include silicon germanium (SiGe), and the second layer 315 may include silicon (Si). In some embodiments, the first and second material compositions have different oxidation rates and / or etch selectivity. As described herein, the second layer 315 can be processed to form nanostructure channels 220 for subsequently formed nanostructure transistors of the semiconductor device 200. The first layer 310 is a sacrificial nanostructure that will eventually be removed and serves to define a vertical distance between adjacent nanostructure channels 220 of the gate structure 240 for the subsequently formed semiconductor device 200. Accordingly, the first layer 310 is referred to as the sacrificial layer, and the second layer 315 can be referred to as the channel layer. Deposition tool 102 deposits and / or grows alternating layers of a stacked layer 305 to include nanostructures (e.g., nanosheets) on a semiconductor substrate 205. For example, deposition tool 102 grows the alternating layers by epitaxial growth. However, other processes can be used to form the alternating layers of the stacked layer 305. Epitaxial growth of the alternating layers of the stacked layer 305 can be performed using molecular beam epitaxy (MBE), metal-organic chemical vapor deposition (MOCVD), and / or other suitable epitaxial growth processes. In some embodiments, an epitaxially grown layer, such as a second layer 315, comprises the same material as the semiconductor substrate 205. In some embodiments, the first layer 310 and / or the second layer 315 comprises a material different from the material of the semiconductor substrate 205. As described above, in some embodiments, the first layer 310 includes an epitaxially grown silicon-germanium (SiGe) layer, and the second layer 315 includes an epitaxially grown silicon (Si) layer. Alternatively, the first layer 310 and / or the second layer 315 may include other materials, such as germanium (Ge); compound semiconductor materials, such as silicon carbide (SiC), gallium arsenide (GaAs), gallium phosphide (GaP), indium phosphide (InP), indium arsenide (IAs), and indium antimonide (InSb); and alloy semiconductors such as silicon germanium (SiGe), gallium arsenide phosphide (GaAsP), aluminum indium arsenide (AlInAs), aluminum gallium arsenide (AlGaAs), indium gallium arsenide (InGaAs), gallium indium phosphide (GaInP), and gallium indium arsenide (GaInP). Phosphide (GaInAsP) and / or combinations thereof. The material of the first layer 310 and / or the material of the second layer 315 can be selected based on providing different oxidation properties, different etch selectivity properties and / or other different properties. As further shown in Figure 3A, the deposition tool 102 may form one or more additional layers over and / or on the stacked layer 305. For example, a hard mask (HM) layer 320 may be formed over and / or on the stacked layer 305 (e.g., on the topmost second layer 315 of the stacked layer 305). As another example, a capping layer 325 may be formed over and / or on the hard mask layer 320. As another example, other hard mask layers including an oxide layer 330 and a nitride layer 335 may be formed over and / or on the capping layer 325. One or more hard mask (HM) layers 320, capping layers 325, and oxide layers 330 may be used to form one or more structures of the semiconductor device 200. The oxide layer 330 can be used as an adhesion layer between the stacked layers 305 and the nitride layer 335, and can also serve as an etch stop layer for etching the nitride layer 335. One or more hard mask layers 320, (capping layer) 325, and (oxide layer) 330 may include silicon germanium (SiGe) and silicon nitride (SiO2). x N y ), silicon oxide (SiO) x The capping layer 325 may include silicon (Si) and / or other materials. In some embodiments, the capping layer 325 is formed of the same material as the semiconductor substrate 205. In some embodiments, one or more additional layers are formed by CVD, PVD, ALD thermal growth, deposition of one or more additional layers, and / or using other deposition techniques. Figure 3B shows a perspective view and a cross-sectional view along line segment AA of the semiconductor device 200. As shown in Figure 3B, the stacked laminate 305 and the semiconductor substrate 205 are etched to remove a portion of the stacked laminate 305 and a portion of the semiconductor substrate 205. The portion 340 of the stacked laminate 305 remaining after the etching operation and the platform portion (also referred to as platform region 210) are referred to as a fin structure 345 on the semiconductor substrate 205 of the semiconductor device 200. The fin structure 345 includes a portion 340 of the stacked laminate 305 over and / or on the platform region 210, which is formed in and / or on the semiconductor substrate 205. The fin structure 345 can be formed using any suitable semiconductor process technology. For example, by using one or more photolithography processes, including double-patterning or multi-patterning processes, the deposition tool 102, exposure tool 104, development tool 106, and / or etching tool can form the fin structure 345. Generally, double-patterning or multi-patterning processes combine photolithography and self-alignment processes, thereby allowing the creation of patterns with, for example, smaller pitches than that achievable using a single and direct photolithography process. For example, a sacrificial layer can be formed over a substrate, and the sacrificial layer can be patterned using a photolithography process. Spacers are formed alongside the patterned sacrificial layer using a self-alignment process. The sacrificial layer is then removed, and the remaining spacers can then be used to pattern the fin structure. In some embodiments, deposition tool 102 forms a photoresist layer over and / or on a hard mask layer including oxide layer 330 and nitride layer 335. Exposure tool 104 exposes the photoresist layer to a radiation source (e.g., deep ultraviolet (UV) radiation, extreme ultraviolet (EUV) radiation), performs a post-exposure bake process (e.g., removes residual solvent from the photoresist layer), and development tool 106 develops the photoresist layer to form a mask element (or pattern) in the photoresist layer. In some embodiments, patterning the photoresist layer to form the mask element is performed using an electron beam (e-beam) photolithography process. The mask element can then be used to protect a portion of semiconductor substrate 205 and a portion of stacked layers 305 during etching operations, such that a portion of semiconductor substrate 205 and a portion of stacked layers 305 remain un-etched to form fin structure 345. Etching (e.g., by means of etching tool 108) the unprotected portions of the substrate and the unprotected portions of the stacked layers 305 forms trenches in the semiconductor substrate 205. The etching tool may use dry etching techniques (e.g., reactive ion etching), wet etching techniques, and / or combinations thereof to etch the unprotected portions of the substrate and the unprotected portions of the stacked layers 305. In some embodiments, other fin-forming techniques are used to form the fin structure 345. For example, fin regions can be defined (e.g., by masking or isolating areas), and said portions 340 can be epitaxially grown as fin structures 345. In some embodiments, forming the fin structure 345 includes a trimming process to reduce the width of the fin structure 345. The trimming process may include wet and / or dry etching processes, etc. As further shown in Figure 3B, fin structures 345 can be formed for different types of nanostructure transistors in the semiconductor device 200. Specifically, a first subset of fin structures 345a can be formed for p-type nanostructure transistors (e.g., p-type metal oxide semiconductor (PMOS) nanostructure transistors), and a second subset of fin structures 345b can be formed for n-type nanostructure transistors (e.g., n-type metal oxide semiconductor (NMOS) nanostructure transistors). The second subset of fin structures 345b can be doped with p-type dopants (e.g., boron (B) and / or germanium (Ge), etc.), and the first subset of fin structures 345a can be doped with n-type dopants (e.g., phosphorus (P) and / or arsenic (As), etc.). Additionally or alternatively, for a p-type nanostructured transistor including a first subset of fin structures 345a, a p-type source / drain region 225 may subsequently be formed, and for an n-type nanostructured transistor including a second subset of fin structures 345b, an n-type source / drain region 225 may subsequently be formed. A first subset of fin structure 345a (e.g., a PMOS fin structure) and a second subset of fin structure 345b (e.g., an NMOS fin structure) can be formed to include similar and / or different characteristics. For example, the first subset of fin structure 345a can be formed as a first height, and the second subset of fin structure 345b can be formed as a second height, wherein the first height and the second height are different heights. As another example, the first subset of fin structure 345a can be formed as a first width, and the second subset of fin structure 345b can be formed as a second width, wherein the first width and the second width are different widths. In the example shown in Figure 3B, the second width of the second subset of fin structure 345b (e.g., for an NMOS nanostructure transistor) is larger than the first width of the first subset of fin structure 345a (e.g., for a PMOS nanostructure transistor). However, other examples are also within the scope of this disclosure. As described above, Figures 3A and 3B are provided as examples. Other examples may differ from those described with reference to Figures 3A and 3B. Compared to the content described with reference to Figures 3A and 3B, exemplary implementation 300 may include additional operations, fewer operations, different operations, and / or operations in a different order. Figures 4A and 4B are diagrams of an exemplary embodiment 400 of the STI formation process described herein. Exemplary embodiment 400 includes an example of forming an STI region 215 for a semiconductor device 200 or a portion thereof between fin structures 345. Semiconductor device 200 may include one or more additional devices, structures, and / or layers not shown in Figures 4A and 4B. Semiconductor device 200 may include additional layers and / or dies formed on layers above and / or below a portion of semiconductor device 200 shown in Figures 4A and 4B. Additionally or alternatively, one or more additional semiconductor structures and / or semiconductor devices may be formed in the same layer of an electronic device including semiconductor device 200. In some embodiments, the operations described in conjunction with exemplary embodiment 400 are performed after the operations described in conjunction with Figures 3A and 3B. Figure 4A shows a perspective view and a cross-sectional view along line segment AA of the semiconductor device 200. As shown in Figure 4A, a liner 405 and a dielectric layer 410 are formed on the semiconductor substrate 205 and interposing (e.g., in between) fin structures 345. A deposition tool 102 can deposit the liner 405 and the dielectric layer 410 on the semiconductor substrate 205 and in trenches between the fin structures 345. The deposition tool 102 can form the dielectric layer 410 such that the height of the top surface of the dielectric layer 410 is approximately the same as the height of the top surface of the nitride layer 335. Alternatively, as shown in Figure 4A, the deposition tool 102 may form a dielectric layer 410 such that the height of the top surface of the dielectric layer 410 is greater than the height of the top surface of the nitride layer 335. In this way, the trenches between the fin structures 345 are overfilled with the dielectric layer 410 to ensure that the trenches are completely filled with the dielectric layer 410. Subsequently, the planarization tool 110 may perform a planarization or polishing operation (e.g., a chemical mechanical polishing (CMP) operation) to planarize the dielectric layer 410. The nitride layer 335 of the hard mask layer can be used as a CMP stop layer during the operation. In other words, the planarization tool 110 planarizes the dielectric layer 410 until it reaches the nitride layer 335 of the hard mask layer. Accordingly, the height of the top surface of the dielectric layer 410 is approximately equal to the height of the top surface of the nitride layer 335 after the operation. The deposition tool 102 can use conformal deposition techniques to deposit the substrate 405. The deposition tool 102 can use CVD techniques (e.g., flowable CVD (FCVD) or other CVD techniques), PVD techniques, ALD techniques, and / or other deposition techniques to deposit the dielectric layer. In some embodiments, after the deposition of the substrate 405, the semiconductor device 200 is annealed, for example, to increase the quality of the substrate 405. Substrate 405 and dielectric layer 410 each include a dielectric material, such as silicon oxide (SiO2). x ), silicon nitride (Si) x N y The dielectric layer 410 may be composed of silicon oxynitride (SiON), fluorine-doped silicate glass (FSG), low-k dielectric materials, and / or other suitable insulating materials. In some embodiments, the dielectric layer 410 may include a multilayer structure, for example, a multilayer structure having one or more substrates. Figure 4B shows a perspective view and a cross-sectional view along line segment AA of the semiconductor device 200. As shown in Figure 4B, an etch-back operation is performed to remove a portion of the substrate 405 and a portion of the dielectric layer 410 to form the STI region 215. An etching tool 108 may etch the substrate 405 and the dielectric layer 410 during the etch-back operation to form the STI region 215. The etching tool 108 etches the substrate 405 and the dielectric layer 410 based on a hard mask layer (e.g., a hard mask layer including an oxide layer 330 and a nitride layer 335). The etching tool 108 etches the substrate 405 and the dielectric layer 410 such that the height of the STI region 215 is less than or approximately equal to the height of the bottom of a portion 340 of the stacked material 305. Accordingly, the portion 340 of the stacked material 305 extends over the STI region 215. In some embodiments, the substrate 405 and dielectric layer 410 are etched such that the height of the STI region 215 is less than the height of the top surface of the platform region 210. In some embodiments, the etching tool 108 uses a plasma-based dry etching technique to etch the substrate 405 and the dielectric layer 410. Ammonia (NH4+) can be used. 3) Hydrofluoric acid (HF) and / or other etchants. Plasma-based dry etching techniques can cause reactions between the etchant and the materials of the substrate 405 and dielectric layer 410, including: Among them, the silicon dioxide (SiO2) of the liner 405 and the dielectric layer 410 2) Reacts with hydrofluoric acid to form silicon tetrafluoride (SiF2). 4) and water (H) Silicon tetrafluoride is a byproduct of hydrofluoric acid and ammonia. It is further broken down by hydrofluoric acid and ammonia to form ammonium fluorosilicate (NH₂O₂). 4) 2SiF 6) Byproducts: Ammonium fluorosilate byproducts are removed from the process chamber of etching tool 108. After removal of ammonium fluorosilate, a post-process temperature in the range of approximately 200 degrees Celsius to approximately 250 degrees Celsius is used to sublimate the ammonium fluorosilate into components of silicon tetrafluoride ammonia and hydrofluoric acid. In some embodiments, the etching tool 108 etches the substrate 405 and the dielectric layer 410 such that the height of the STI region 215 between a first subset of fin structures 345a (e.g., for a PMOS nanostructure transistor) is greater than the height of the STI region 215 between a second subset of fin structures 345b (e.g., for an NMOS nanostructure transistor). This is primarily due to the fact that the width of the fin structure 345b is greater than the width of the fin structure 345a. Furthermore, this results in the top surface of the STI region 215 between fin structures 345a and fin structures 345b being sloped or slanted (e.g., downward sloped from fin structure 345a to fin structure 345b, as illustrated in Figure 4A). Due to the van der Waals forces between the etchant and the surfaces of the substrate 405 and dielectric layer 410, the etchant used to etch the substrate 405 and dielectric layer 410 first undergoes physisorption (e.g., physical bonding) to the substrate 405 and dielectric layer 410. The etchant is trapped by a dipole movement force. Then, the etchant attaches to the dangling bonds of the substrate 405 and dielectric layer 410, initiating chemisorption. Here, the chemisorption of the etchant on the surfaces of the substrate 405 and dielectric layer 410 causes the substrate 405 and dielectric layer 410 to be etched. The greater width of the trenches between the second subsets of the fin structure 345b provides a larger surface area for chemisorption to occur, resulting in a greater etching rate between the second subsets of the fin structure 345b. The higher etching rate results in a smaller height for the STI region 215 between the second subset of fin structure 345b compared to the height for the STI region 215 between the first subset of fin structure 345a. As described above, Figures 4A and 4B are provided as examples. Other examples may differ from those described with reference to Figures 4A and 4B. Compared to the content described with reference to Figures 4A and 4B, exemplary implementation 400 may include additional operations, fewer operations, different operations, and / or operations in a different order. Figures 5A through 5C are illustrations of an exemplary embodiment 500 of the sidewall covering process described herein. Exemplary embodiment 500 includes an example of forming a sidewall covering over a portion 340 of a stacked matrix 305 for a semiconductor device 200 or a portion thereof. The semiconductor device 200 may include one or more additional devices, structures, and / or layers not shown in Figures 5A through 5C. The semiconductor device 200 may include additional layers and / or dies formed on layers above and / or below a portion of the semiconductor device 200 shown in Figures 5A through 5C. Additionally or alternatively, one or more additional semiconductor structures and / or semiconductor devices may be formed in the same layer of an electronic device including the semiconductor device 200. In some embodiments, the operations described in conjunction with exemplary embodiment 500 are performed after the operations described in conjunction with Figures 3A, 3B, 4A, and 4B. Figure 5A shows a perspective view and a cross-sectional view along line segment AA of the semiconductor device 200. As shown in Figure 5A, a cladding layer 505 is formed over the fin structure 345 (e.g., above the top surface and sidewalls of the fin structure 345) and over the STI region 215 between the fin structures 345. The cladding layer 505 comprises silicon germanium (SiGe) or other materials. The cladding layer 505 may be formed of the same material as the first layer 310 so that the cladding sidewalls (from which the cladding layer 505 will be formed) and the first layer 310 can be removed in the same etching operation (nanostructure release operation), thereby allowing an alternative gate (e.g., gate structure 240) to be formed in the region occupied by the cladding sidewalls and the first layer 310. This allows the alternative gate to fully surround the nanostructure channel of the nanostructure transistor of the semiconductor device 200. Deposition tool 102 can deposit the cladding layer 505. In some embodiments, deposition tool 102 deposits a seed layer (e.g., a silicon (Si) seed layer or other type of seed layer) over the fin structure 345 (e.g., above the top surface and sidewalls of the fin structure 345) and over the STI region 215 between the fin structures 345. Then, deposition tool 102 deposits silicon-germanium on the seed layer to form the cladding layer 505. The seed layer promotes the growth and adhesion of the cladding layer 505. The deposition of seed layers may include the use of gases such as nitrogen (N) 2) or hydrogen (H) 2) A carrier gas, etc., provides silicon precursors to the process chamber of the deposition tool 102. In some embodiments, a pre-cleaning operation is performed before depositing the seed layer to reduce germanium oxide (GeO). x The formation of silicon precursors. Silicon precursors may include silane (Si). 2H 6) or other silicon precursors. The use of ethylene silane enables the formation of seed layers with a thickness ranging from about 0.5 nanometers to about 1.5 nanometers to provide sufficient coating sidewall thickness while achieving a controllable and uniform thickness of the coating layer 505. However, other ranges and values ​​for the thickness of the seed layer are also within the scope of this disclosure. Seed layer deposition can be performed at temperatures ranging from approximately 450 degrees Celsius to approximately 500 degrees Celsius (or other temperature ranges), at pressures ranging from approximately 30 to approximately 100 to approximately 100 to approximately 100 to approximately 100 to approximately 100 seconds (or other durations), etc. The deposition of silicon-germanium cladding layer 505 may include forming cladding layer 505 to include an amorphous texture to promote conformal deposition of cladding layer 505. Silicon-germanium may include a germanium content ranging from approximately 15% to approximately 25%. However, other values ​​for germanium content are also within the range disclosed herein. The deposition of cladding layer 505 may include the use of a gas such as nitrogen (N2). 2) or hydrogen (H) 2) etc., carrier gas, to provide silicon precursor (e.g., ethylene silane (Si)) to the process chamber of deposition tool 102. 2H 6) or silicon tetrahydride (SiH) 4) etc.) and germanium precursors (e.g., germanium tetrahydride, GeH 4) or other germanium precursors). The deposition of the coating layer 505 can be performed at a temperature (or other temperature range) in the range of about 500 degrees Celsius to about 550 degrees Celsius and / or at a pressure (or other pressure range) in the range of about 5 Torr to about 20 Torr. Figure 5B shows a perspective view and a cross-sectional view along line segment AA of the semiconductor device 200. As shown in Figure 5B, an etch-back operation is performed to etch the cladding layer 505 to form cladding sidewalls 510. The etching tool 108 may use plasma-based dry etching techniques or other etching techniques to etch the cladding layer 505. The etching tool 108 may perform an etch-back operation to remove a portion of the cladding layer 505 from the tops of the fin structures 345 and from the tops of the STI regions 215. Removing the cladding layer 505 from the tops of the STI regions 215 between the fin structures 345 ensures that the cladding sidewalls 510 do not include footing located on the STI regions 215 between the fin structures 345. This ensures that the cladding sidewalls 510 do not include footing below the hybrid fin structure, which will be formed above the STI regions 215 between the fin structures 345. In some embodiments, the etching tool 108 uses a fluorine-based etchant to etch the coating layer 505. Fluorine-based etchants may include sulfur hexafluoride (SF6). 6) Fluoromethane (CH4) 3F 3) and / or other fluorine-based etchants. Other reactants and / or supports, such as methane (CH4), can be used in the etch-back operation. 4) Hydrogen (H) 2) Argon (Ar) and / or helium (He). In some embodiments, a plasma bias in the range of approximately 500 volts to approximately 2000 volts is used to perform the etch-back operation. However, other values ​​of plasma bias are also within the range of this disclosure. In some embodiments, a portion of removing the cladding layer 505 from the top of the STI region 215 includes performing highly directional (e.g., anisotropic) etching to selectively remove (e.g., selectively etch) the cladding layer 505 on top of the STI region 215 between the fin structures 345. In some embodiments, the cover sidewall 510 includes asymmetric characteristics (e.g., different lengths, depths, and / or angles). The asymmetric characteristics can provide increased depth of the gate structure 240 for different types of nanostructured transistors (e.g., for p-type nanostructured transistors, for n-type nanostructured transistors), while reducing and / or minimizing the base of the cover sidewall 510 in the STI region beneath the hybrid fins of the nanostructured transistor of the semiconductor device 200 (and thus, after removing the cover sidewall 510, reducing and / or minimizing the pins of the gate structure 240 formed in the region occupied by the cover sidewall 510). Reduced and / or minimized pins further reduce the likelihood of electrical shorting and / or leakage current. Figure 5C shows a perspective view and a cross-sectional view along line segment AA of the semiconductor device 200. As shown in Figure 5C, the hard mask layer (including oxide layer 330 and nitride layer 335) and the capping layer 325 are removed to expose the hard mask layer 320. In some embodiments, etching operations (e.g., performed by etching tool 108), planarization techniques (e.g., performed by planarization tool 110), and / or other semiconductor process techniques are used to remove the capping layer 325, oxide layer 330, and nitride layer 335. As described above, Figures 5A to 5C are provided as examples. Other examples may differ from those described with reference to Figures 5A to 5C. Compared to the content described with reference to Figures 5A to 5C, exemplary implementation 500 may include additional operations, fewer operations, different operations, and / or operations in a different order. Figures 6A through 6C are diagrams of an exemplary embodiment 600 of the hybrid fin structure fabrication process described herein. Exemplary embodiment 600 includes an example of forming a hybrid fin structure between fin structures 345 for a semiconductor device 200 or a portion thereof. The semiconductor device 200 may include one or more additional devices, structures, and / or layers not shown in Figures 6A through 6C. The semiconductor device 200 may include additional layers and / or grains formed on layers above and / or below a portion of the semiconductor device 200 shown in Figures 6A through 6C. Additionally or alternatively, one or more additional semiconductor structures and / or semiconductor devices may be formed in the same layer of an electronic device including the semiconductor device 200. In some embodiments, the operations described in conjunction with exemplary embodiment 600 are performed after the operations described in conjunction with Figures 3A, 3B, 4A, 4B, and 5A through 5C. Figure 6A shows a perspective view and a cross-sectional view along line segment AA of the semiconductor device 200. As shown in Figure 6A, a substrate 605 and a dielectric layer 610 are formed over and above the STI region 215 of the interposed (e.g., in between) fin structure 345. Deposition tool 102 can deposit the substrate 605 and the dielectric layer 610. The deposition tool 102 can use conformal deposition techniques to deposit the substrate 605. The deposition tool 102 can use CVD techniques (e.g., flow CVD (FCVD) or other CVD techniques), PVD techniques, ALD techniques, and / or other deposition techniques to deposit the dielectric layer 610. In some embodiments, after depositing the dielectric layer 610, the semiconductor device 200 is annealed, for example, to improve the quality of the dielectric layer 610. The deposition tool 102 can form a dielectric layer 610 such that the height of the top surface of the dielectric layer 610 is approximately the same as the height of the top surface of the hard masking layer 320. Alternatively, as shown in the example in Figure 6A, the deposition tool 102 can form a dielectric layer 610 such that the height of the top surface of the dielectric layer 610 is greater than the height of the top surface of the hard masking layer 320. In this way, the trenches between the fin structures 345 are overfilled with the dielectric layer 610 to ensure that the trenches are completely filled with the dielectric layer 610. Subsequently, the planarization tool 110 can perform a planarization or polishing operation (e.g., a CMP operation) to planarize the dielectric layer 610. Substrate 605 and dielectric layer 610 each include a dielectric material, such as silicon oxide (SiO2). x ), silicon nitride (Si) x N y Silicon oxynitride (SiON), silicon carbonitride (SiCN), fluorine-doped silicate glass (FSG), low-k dielectric materials, and / or other suitable insulating materials. In some embodiments, dielectric layer 610 may include a multilayer structure, for example, a multilayer structure having one or more substrates. Figure 6B shows a perspective view and a cross-sectional view along line segment AA of the semiconductor device 200. As shown in Figure 6B, an etch-back operation is performed to remove a portion of the dielectric layer 610. The etching tool 108 may etch the dielectric layer 610 during the etch-back operation to reduce the height of the top surface of the dielectric layer 610. In particular, the etching tool 108 etches the dielectric layer 610 such that the height of a portion of the dielectric layer 610 between the fin structures 345 is less than the height of the top surface of the hard mask layer 320. In some embodiments, the etching tool 108 etches the dielectric layer 610 such that the height of a portion of the dielectric layer 610 between the fin structures 345 is approximately equal to the height of the top surface of the top-most of the second layers 315 of said portion 340. Figure 6C shows a perspective view and a cross-sectional view along line segment AA of the semiconductor device 200. As shown in Figure 6C, a high dielectric constant (high k) layer 615 is deposited over a portion of the dielectric layer 610 between the fin structures 345. The deposition tool 102 can use CVD, PVD, ALD, and / or other deposition techniques to deposit materials such as hafnium oxide (HfO). x A high-k material and / or other high-k dielectric material are used to form a high-k layer 615. A combination of a portion of the dielectric layer 610 between the fin structures 345 and the high-k layer 615 between the fin structures 345 is referred to as a hybrid fin structure 620 (or dummy fin structure). In some embodiments, a planarization tool 110 may perform a planarization operation to planarize the high-k layer 615 such that the height of the top surface of the high-k layer 615 is approximately equal to the height of the hard mask layer 320. Subsequently, as shown in Figure 6C, the hard mask layer 320 is removed. Removing the hard mask layer 320 may include using etching techniques (e.g., plasma etching, wet chemical etching, and / or other types of etching techniques) or other removal techniques. As described above, Figures 6A through 6C are provided as examples. Other examples may differ from those described with reference to Figures 6A through 6C. Compared to the content described with reference to Figures 6A through 6C, exemplary implementation 600 may include additional operations, fewer operations, different operations, and / or operations in a different order. Figures 7A and 7B are diagrams of an exemplary embodiment 700 of the dummy gate formation process described herein. Exemplary embodiment 700 includes an example of forming a dummy gate structure for a semiconductor device 200 or a portion thereof. Semiconductor device 200 may include one or more additional devices, structures, and / or layers not shown in Figures 7A and 7B. Semiconductor device 200 may include additional layers and / or dies formed on layers above and / or below a portion of semiconductor device 200 shown in Figures 7A and 7B. Additionally or alternatively, one or more additional semiconductor structures and / or semiconductor devices may be formed in the same layer of an electronic device including semiconductor device 200. In some embodiments, the operations described in conjunction with exemplary embodiment 700 are performed after the operations described in conjunction with Figures 3A, 3B, 4A, 4B, 5A through 5C, and 6A through 6C. Figure 7A shows a perspective view of semiconductor device 200. As shown in Figure 7A, a dummy gate structure 705 (also called a dummy gate stack or temporary gate structure) is formed above fin structure 345 and hybrid fin structure 620. The dummy gate structure 705 is a sacrificial structure that will be replaced by an alternative gate structure or alternative gate stack (e.g., gate structure 240) at a later process stage of semiconductor device 200. A portion of the underlying fin structure 345 may be referred to as a channel region. The dummy gate structure 705 may also define source / drain (S / D) regions of fin structure 345, such as regions adjacent to the channel region and on opposite sides of the channel region. The dummy gate structure 705 may include a gate electrode layer 710, a hard masking layer 715 above and / or on the gate electrode layer 710, and spacer layers 720 on both sides of the gate electrode layer 710 and the hard masking layer 715. The dummy gate structure 705 may be formed on the gate dielectric layer 725 between the topmost second layer 315 and the dummy gate structure 705, and between the hybrid fin structure 620 and the dummy gate structure 705. The gate electrode layer 710 includes polycrystalline silicon (PO) or other materials. The hard masking layer 715 includes one or more layers, such as oxide layers (e.g., may include silicon dioxide (SiO2)). 2) or other materials (pad oxide layer) and a nitride layer formed on top of the oxide layer (e.g., may include Si) 3N 4. A pad nitride layer of silicon nitride or other materials. Spacer layer 720 includes silicon oxide (SiOC), nitrogen-free SiOC, or other suitable materials. Gate dielectric layer 725 may include silicon oxide (e.g., such as SiO₂). 2SiO x ), silicon nitride (e.g., such as Si), 3N 4 of Si x N y ), high-k dielectric materials and / or other suitable materials. The layer of the dummy gate structure 705 can be formed using various semiconductor manufacturing processes, such as deposition (e.g., using deposition tool 102), patterning (e.g., using exposure tool 104 and development tool 106), and / or etching (e.g., using etching tool 108), etc. Examples include CVD, PVD, ALD, thermal oxidation, electron beam evaporation, photolithography, electron beam photolithography, photoresist coating (e.g., spin-on coating), soft baking, mask alignment, exposure, post-exposure baking, photoresist development, rinsing, drying (e.g., spin-drying and / or hard baking), dry etching (e.g., reactive ion etching), and / or wet etching, etc. In some embodiments, a gate dielectric layer 725 is conformally deposited on the semiconductor device 200 and then selectively removed from a portion of the semiconductor device 200 (e.g., a source / drain region). A gate electrode layer 710 is then deposited on the remaining portion of the gate dielectric layer 725. A hard mask layer 715 is then deposited on the gate electrode layer 710. A spacer layer 720 can be conformally deposited in a similar manner as the gate dielectric layer 725, and the spacer layer 720 can be etched back such that the spacer layer 720 remains on the sidewalls of the dummy gate structure 705. In some embodiments, the spacer layer 720 includes a plurality of types of spacer layers. For example, the spacer layer 720 may include a seal spacer layer formed on the sidewalls of the dummy gate structure 705 and a bulk spacer layer formed on the seal spacer layer. The sealing spacer layer and the bulk spacer layer can be formed from similar or different materials. In some embodiments, the bulk spacer layer is formed without using plasma surface treatment for the sealing spacer layer. In some embodiments, the bulk spacer layer is formed to a thickness greater than that of the sealing spacer layer. In some embodiments, the gate dielectric layer 725 is omitted from the dummy gate structure forming process and is instead formed in an alternative gate process. Figure 7A further illustrates the reference cross-sections used in the following figures as described herein. Cross-section AA is in the xz plane (referred to as the y-cut) across the fin structure 345 and hybrid fin structure 620 in the source / drain regions of semiconductor device 200. Cross-section BB is in the yz plane (referred to as the x-cut) perpendicular to cross-section AA, and crosses the dummy gate structure 705 in the source / drain regions of semiconductor device 200. Cross-section CC is in the xz plane parallel to cross-section AA and perpendicular to cross-section BB, and follows the dummy gate structure 705. For clarity, the following figures refer to these reference cross-sections. In some figures, for ease of depiction, some component symbols for the components or parts shown may be omitted to avoid confusion with other components or parts. Figure 7B includes cross-sectional views along sections AA, BB, and CC of Figure 7A. As shown in sections BB and CC of Figure 7B, a dummy gate structure 705 is formed above the fin structure 345. As shown in section CC of Figure 7B, a portion of the gate dielectric layer 725 and a portion of the gate electrode layer 710 are formed in a recess above the fin structure 345, and the recess is formed by removing the hard masking layer 320. As described above, Figures 7A and 7B are provided as examples. Other examples may differ from those described with reference to Figures 7A and 7B. Compared to the content described with reference to Figures 7A and 7B, exemplary implementation 700 may include additional operations, fewer operations, different operations, and / or operations in a different order. Figures 8A through 8D are diagrams of an exemplary embodiment 800 of the source / drain recess formation process and the inner spacer formation process described herein. Exemplary embodiment 800 includes an example of forming source / drain recesses and inner spacers 245 for a semiconductor device 200. Figures 8A through 8D are shown from a plurality of perspective views shown in Figure 7A, including a perspective view of cross-section AA in Figure 7A, a perspective view of cross-section BB in Figure 7A, and a perspective view of cross-section CC in Figure 7A. In some embodiments, the operations described in conjunction with exemplary embodiment 800 are performed after the operations described in conjunction with Figures 3A, 3B, 4A, 4B, 5A through 5C, 6A through 6C, and 7A and 7B. As shown in cross-sections AA and BB of Figure 8A, during the etching operation, source / drain recesses 805 are formed in a portion 340 of the fin structure 345. The source / drain recesses 805 are formed to provide space in which source / drain regions 225 are formed on both sides of the dummy gate structure 705. The etching operation can be performed by etching tool 108 and can be referred to as a strained source / drain (SSD) etching operation. In some embodiments, the etching operation includes plasma etching, wet chemical etching, and / or other types of etching techniques. The source / drain recess 805 also extends into a portion of the platform region 210 of the fin structure 345. As a result, a plurality of platform regions 210 are formed in each fin structure 345, wherein a portion of the sidewall of each source / drain recess 805 below said portion 340 corresponds to the sidewall of the platform region 210. The source / drain recess 805 can penetrate into the well portion (e.g., p-well, n-well) of the fin structure 345. In embodiments where the semiconductor substrate 205 comprises silicon (Si) material with (100) orientation, (111) faces are formed at the bottom of the source / drain recess 805, resulting in a V-shape or triangular cross-section at the bottom of the source / drain recess 805. In some embodiments, a V-shaped profile is formed using wet etching with tetramethylammonium hydroxide (TMAH) and / or chemical dry etching with hydrochloric acid (HCl). However, the profile at the bottom of the source / drain recess 805 may include other shapes, such as round or semi-circular, etc. As shown in cross-sections BB and CC of Figure 8A, after the etching operation, a portion of the first layer 310 and a portion of the second layer 315 of the stacked layers 305 are retained below the dummy gate structure 705 to form source / drain recesses 805. A portion of the second layer 315 below the dummy gate structure 705 forms a nanostructure channel 220 of the nanostructure transistor of the semiconductor device 200. The nanostructure channel 220 extends between adjacent source / drain recesses 805 and between adjacent hybrid fin structures 620. As shown in section BB of Figure 8B, during the etching operation, the first layer 310 is etched laterally (e.g., in a direction approximately parallel to the length of the first layer 310) to form cavities 810 between portions of the nanostructure channels 220. Specifically, the etching tool 108 etches laterally through the source / drain recess 805 at the end of the first layer 310 below the dummy gate structure 705 to form cavities 810 between the ends of the nanostructure channels 220. In embodiments where the first layer 310 is silicon-germanium (SiGe) and the second layer 315 is silicon (Si), the etching tool 108 can selectively etch the first layer 310 using a wet etchant, such as hydrogen peroxide (H₂O). 2O 2) Acetic acid (CH4) A mixed solution of 3COOH and / or hydrogen fluoride (HF), then diluted with water (H2O). 2O) Cleaning. A mixed solution and water may be provided to the source / drain recess 805 to etch the first layer 310 from the source / drain recess 805. In some embodiments, the etching with the mixed solution and the rinsing with water are repeated approximately 10 to approximately 20 times. In some embodiments, the etching time with the mixed solution is in the range of approximately 1 minute to approximately 2 minutes. The mixed solution can be used at temperatures in the range of approximately 60 degrees Celsius to approximately 90 degrees Celsius. However, other values ​​for the parameters of the etching operation are also within the range of this disclosure. The cavity 810 can be formed in an approximately curved shape, an approximately triangular shape, an approximately square shape, or other shapes. In some embodiments, the depth of one or more cavities 810 (e.g., the size of the cavity extending from the source / drain recess 805 into the first layer 310) is in the range of approximately 0.5 nanometers to approximately 5 nanometers. In some embodiments, the depth of one or more cavities 810 is in the range of approximately 1 nanometer to approximately 3 nanometers. However, other values ​​for the depth of the cavity 810 are also within the range of this disclosure. In some embodiments, the etching tool 108 forms the cavity 810 to a certain length (e.g., the size of the cavity extends from the nanostructure channel 220 below the first layer 310 to another nanostructure channel 220 above the first layer 310) such that the cavity 810 partially extends to the sides of the nanostructure channel 220 (e.g., such that the width or length of the cavity 810 is greater than the thickness of the first layer 310). In this way, the internal spacer formed in the cavity 810 can extend into a portion of the end of the nanostructure channel 220. In some embodiments, forming the cavity 810 results in thinning of the cladding sidewall 510 in the source / drain recess 805. As shown in cross-sections AA and BB of Figure 8C, an insulating layer 815 is conformally deposited along the bottom of the source / drain recess 805 and along the sidewalls of the source / drain recess 805. The insulating layer 815 further extends along the spacer layer 720. The deposition tool 102 can be used to deposit the insulating layer 815 using CVD, PVD, ALD, and / or other deposition techniques. The insulating layer 815 comprises silicon nitride (Si). x N y ), silicon oxide (SiO) x Silicon oxynitride (SiON), silicon oxycarbonate (SiOC), silicon carbonitride (SiCN), silicon oxycarbonitride (SiOCN), and / or other dielectric materials. The insulating layer 815 may include a material different from that of the spacer layer 720. The deposition tool 102 forms an insulating layer 815 of sufficient thickness to fill the cavity 810 between the nanostructure channels 220. For example, the insulating layer 815 can be formed to a thickness ranging from about 1 nanometer to about 10 nanometers. As another example, the insulating layer 815 is formed to a thickness ranging from about 2 nanometers to about 5 nanometers. However, other values ​​for the thickness of the insulating layer 815 are also within the scope of this disclosure. As shown in cross-sections AA and BB in Figure 8D, the insulating layer 815 is partially removed such that the remaining portion of the insulating layer 815 corresponds to the inner spacer 245 in the cavity 810. An etching tool 108 can perform an etching operation to partially remove the insulating layer 815. As further shown in cross-section AA in Figure 8D, the covering sidewall 510 can also be removed from the source / drain recess 805 during the etching operation to partially remove the insulating layer 815. In some embodiments, the etching operation may cause the surface of the inner spacer 245 facing the source / drain recess 805 to be curved or recessed. The depth of the recess in the inner spacer 245 may range from about 0.2 nanometers to about 3 nanometers. As another example, the depth of the recess in the inner spacer 245 may range from about 0.5 nanometers to about 2 nanometers. As another example, the depth of the recess in the inner spacer 245 may be less than about 0.5 nanometers. In some embodiments, the surface of the inner spacer 245 facing the source / drain recess 805 is approximately flat, such that the surface of the inner spacer 245 and the surface of the end of the nanostructure channel 220 are approximately even and flush. As described above, Figures 8A to 8D are provided as examples. Other examples may differ from those described with reference to Figures 8A to 8D. Compared to the content described with reference to Figures 8A to 8D, exemplary implementation 800 may include additional operations, fewer operations, different operations, and / or operations in a different order. Figures 9A through 9F are diagrams illustrating exemplary embodiments of the source / drain region formation process described herein. Exemplary embodiments include examples of shaping the nanostructure channel 220 (e.g., forming a recess in the second layer 315). Exemplary embodiment 900 also includes an example of forming the source / drain region 225 in the source / drain recess 805 of the semiconductor device 200 after shaping the nanostructure channel 220. Figures 9A through 9F are shown from a plurality of perspective views illustrated in Figure 7A, and include a perspective view of cross-section AA, cross-section BB, and cross-section CC in Figure 7A. In some embodiments, the operations described in conjunction with Exemplary Embodiment 900 are performed after the operations described in conjunction with Figures 3A, 3B, 4A, 4B, 5A to 5C, 6A to 6C, 7A, 7B, and 8A to 8D. Figure 9A shows a cross-sectional view BB of an exemplary portion of region 905 of semiconductor device 205, which includes source / drain recesses 805 (e.g., recesses for forming source / drain regions 225). Example 910 on the left side of Figure 9A shows a portion of region 905 after an epitaxial layer 915 has been deposited within the source / drain recesses 805. In some embodiments, the epitaxial layer 915 (e.g., the "L0" layer) corresponds to buffer region 230. Deposition tool 102 deposits an epitaxial layer 915 to include one or more dimensional characteristics. As an example, and after deposition, the thickness D1 of the epitaxial layer 915 can range from approximately 10 nanometers to approximately 50 nanometers. Additionally or alternatively, the height D2 (e.g., "raise height") of the epitaxial layer 915 above the bottom-most layer of the first layer 310 can range from approximately 3 nanometers to approximately 5 nanometers. However, other values ​​and ranges for thickness D1 and height D2 are also within the scope of this disclosure. Epitaxial layer 915 (e.g., buffer region 230) may include different materials. For example, epitaxial layer 915 may include silicon (Si) material. Additionally or alternatively, epitaxial layer 915 may include silicon-germanium (e.g., SiGe) material. When epitaxial layer 915 includes silicon-germanium material, the germanium content in epitaxial layer 915 may include a range of approximately 5% to approximately 20%. However, other materials and / or other values ​​and ranges of germanium content in epitaxial layer 915 are also within the scope of this disclosure. Example 920 on the right side of Figure 9A shows a portion of region 905 after an etching operation. As an example, etching tool 108 can perform an etching operation to remove (e.g., trim) a portion of epitaxial layer 915. The etching operation can alter one or more dimensional characteristics of epitaxial layer 915. For example, and as a result of the etching operation, the thickness D3 of epitaxial layer 915 can be reduced (e.g., relative to thickness D1) to include a range of approximately 8 nanometers to approximately 40 nanometers. If the thickness D3 (post-etching) is less than approximately 8 nanometers, the size of epitaxial layer 915 (e.g., buffer region 230) may be insufficient to prevent leakage current in nanostructured transistors. If the thickness is greater than approximately 40 nanometers, the volume of the epitaxial layer subsequently formed within the source / drain recess 805 can be reduced, increasing parasitic resistance within the nanostructured transistor. However, other values ​​and ranges of the thickness D3 of epitaxial layer 915 (post-etching) are also within the scope of this disclosure. Additionally or alternatively, the height D4 of the epitaxial layer 915 (e.g., the height increase after etching) can be reduced (e.g., relative to the thickness D3) to include a range of approximately 1 nanometer to approximately 3 nanometers. However, other values ​​and ranges of the height D4 of the epitaxial layer 915 (after etching) are also within the scope of this disclosure. As further illustrated in Example 920 on the right side of Figure 9A, the etching operation forms a concave region 925 in the end of the second layer 315 (e.g., in the end of the channel layer). The etching tool 108 can perform the etching operation using a recipe that includes a particular flow profile (e.g., a cyclic flow profile) and / or the concentration of the etchant, etc. The recipe can be configured such that the duration of contact between the etchant and the surface at or near the lower regions of the source / drain recess 805 is longer than the duration of contact with the surface at or near the upper regions of the source / drain recess 805, which may result in a variation in the size (e.g., depth) of the concave region 925 (e.g., the depth of a concave region near the top of the source / drain recess 805 may be smaller than the depth of another concave region near the bottom of the source / drain recess 805). In some implementations, the concave region 925 reduces the likelihood of non-coupling issues in the subsequently formed epitaxial layers of the source / drain regions 225. For example, it can reduce or eliminate voids within the subsequently formed epitaxial layers. Furthermore, the concave region 925 can reduce the length of the nanostructure channels, thereby reducing the channel resistance (Ro) of the nanostructure transistor. ch Additionally or alternatively, the volume of the epitaxial material within the source / drain region 225 can be increased to reduce the parasitic resistance (R0) of the nanostructured transistor. p ). In some embodiments, and after the etching operation, a cleaning operation may be performed to remove residual etchant and / or etched material. As an example, a cleaning tool may dispense a cleaning solution into the source / drain recess 805 to remove residual etchant, residual particles from the etched epitaxial layer 915, and / or residual particles from the ends of the etched second layer 315. Figure 9B shows an isometric view of an exemplary portion of region 905, including gate electrode layer 710 and spacer layer 720. As shown in Figure 9B, the end of the first layer 310 (e.g., sacrificial layer) includes an inner spacer 245, and the end of the second layer 315 (e.g., channel layer) includes a concave region 925. In some embodiments, the distance D5 from the apex of the concave region 925 to the edge of the gate electrode layer 710 may correspond to the proximity of the source / drain region 225 (e.g., the subsequently formed source / drain region) to a portion of the gate structure 240 (e.g., the subsequently formed gate structure). Proximity may be related to one or more performance characteristics of the nanostructure transistor including the concave region 925 (e.g., channel resistance (R)). ch This is related to (and / or short-channel effect (SCE), etc.) and can be improved by using concave regions to reduce distance D5 (e.g., proximity). Figure 9C shows a cross-sectional view BB of an exemplary portion of region 905. Figure 9C includes second layers 315a-315c alternating with the first layers 310a and 310b. Figure 9C also includes concave regions 925a-925c and inner spacers 245a and 245b. As shown in Figure 9C, a portion of region 905 may include one or more dimensional characteristics and / or dimensional relationships. For example, the thicknesses of the second layers 315a to 315c can be different. For instance, the thickness D6 of the second layer 315a can be smaller than the thickness D7 of the second layer 315b, where the difference ranges from approximately 0.2 nanometers to approximately 1.0 nanometers. Additionally or alternatively, the thickness D7 of the second layer 315b can be smaller than the thickness D8 of the second layer 315c, where the difference ranges from approximately 0.2 nanometers to approximately 1.5 nanometers. However, other values ​​and ranges of the differences in thicknesses D6, D7, and D8 are also within the scope of this disclosure. Additionally or alternatively, the thickness ratio of the first layers 310a and 310b to the second layers 315a-315c can be varied. For example, the ratio of the thickness D9 of the first layer 310a (and / or the thickness D10 of the first layer 310b) to the thickness D6 of the second layer 315a (and / or the thickness D7 of the second layer 315b, and / or the thickness D8 of the second layer 315c) can be in the range of about 1 to about 2. If the ratio is less than about 1, the charge collection for channel operation (e.g., the channel formed by the second layers 315a-315c) in the nanostructure transistor can be reduced. If the ratio is greater than about 2, the available area for gate formation (e.g., after removing the first layers 310a and 310b) may be reduced, resulting in defects in the gate structure formation. However, other values ​​and ranges of the ratios of thicknesses D9, D10 to thicknesses D6, D7 and D8 are also within the scope of this disclosure. Additionally or alternatively, the depths of concave regions 925a-925c may be different. For example, the depth D11 of concave region 925a may be greater than the depth D12 of concave region 925c, where the difference is in the range of approximately 0.5 nm to approximately 1.5 nm (e.g., as shown in Figure 9C, concave region 925a, i.e., the first concave region, is located below concave region 925c, i.e., the second concave region). Additionally or alternatively, the depth D13 of concave region 925b may be greater than the depth D12 of concave region 925c, where the difference is in the range of approximately 0.5 nm to approximately 1.0 nm. However, other values ​​and ranges of the differences in depths D11, D12, and D13 are also within the scope of this disclosure. The angles associated with concave region 925 (e.g., angle D14 defining concave region 925a, angle D15 defining concave region 925c, etc.) can range from approximately 120 degrees to approximately 160 degrees. If the angles associated with one or more of the concave regions 925a-925c are less than approximately 120 degrees, void defects may occur in the epitaxial layer of the subsequently formed source / drain regions (e.g., source / drain region 225). If the angles are greater than approximately 160 degrees, the increase in volume of the epitaxial layer in the subsequently formed source / drain regions may not increase, thus failing to reduce the parasitic resistance in the nanostructured transistor. Additionally or alternatively, the angle associated with the concave region 925 can be varied. As an example, the angle D14 can be smaller relative to the angle D15, where the difference ranges from approximately 5 degrees to approximately 15 degrees. However, other values ​​and ranges defining the angle of the concave region 925 and the differences between angles are also within the scope of this disclosure. Figure 9D shows a cross-sectional view BB of an exemplary portion of region 905 after the formation of source / drain region 225. Forming source / drain region 225 may include depositing a seed layer 930 using CVD, ALD, PVD, and / or other deposition techniques, followed by depositing an epitaxial layer 935 over the seed layer 930. The seed layer 930 (e.g., a silicon boron seed layer, etc.) may facilitate the growth (e.g., deposition) of the epitaxial layer 935 in concave region 925. Epitaxial layer 935 (e.g., the first epitaxial layer of source / drain region 225, which may be referred to as "L1-1" layer) may include a portion 935a located above buffer region 230 (e.g., above epitaxial layer 915 and within buffer region), and convex-shaped portions 935b in concave region 925 at the end of second layer 315 (e.g., at the end of a plurality of channel layers). As an example, epitaxial layer 935 may include silicon material doped with boron (e.g., SiB). In this case, the boron doping concentration may be approximately 1 x 10⁻⁶ per cubic centimeter. 20 From atoms per cubic centimeter to approximately 8 x 10^6 atoms per cubic centimeter. 20 Within the range of atoms. However, other combinations of materials, dopants, and doping concentration ranges used for epitaxial layer 935 are also within the scope of this disclosure. In some embodiments, and as shown, the thickness D16 of the convex portion 935b can range from about 2 nanometers to about 5 nanometers. If the thickness D16 is less than about 2 nanometers, the convex portion 935b may be ineffective in shielding the dopants of the source / drain region 225 from the second layer 315 (e.g., the channel layer). If the thickness D16 is greater than about 5 nanometers, the volume of the epitaxial material in the source / drain region 225 may not increase (and the parasitic resistance of the nanostructured transistor cannot be reduced). However, other values ​​and ranges of the thickness D16 are also within the scope of this disclosure. Figure 9D further shows the epitaxial layer 940 above the epitaxial layer 935 (e.g., the second epitaxial layer of the source / drain region 225, which may be referred to as the "L1-2" layer). The epitaxial layer 940 may include a thickness ranging from approximately 5 nanometers to approximately 15 nanometers, etc. Furthermore, the epitaxial layer 940 may include boron-doped silicon germanium material (e.g., SiGeB). In this case, the germanium (Ge) concentration in the epitaxial layer 940 may range from approximately 10% germanium to approximately 30% germanium. The boron doping concentration may be approximately 1 x 10⁻⁶ per cubic centimeter. 20 From one atom to approximately 5 x 10^6 atoms per cubic centimeter. 20 Within the range of atoms. However, other combinations of the thickness, material, dopants, and doping concentration range of the epitaxial layer 940 are also within the scope of this disclosure. Figure 9D further shows the epitaxial layer 945 above the epitaxial layer 940 (e.g., the third epitaxial layer of the source / drain region 225, which may be referred to as the "L2" layer). The epitaxial layer 945 may include a thickness ranging from approximately 10 nanometers to approximately 40 nanometers, etc. Furthermore, the epitaxial layer 945 may include boron-doped silicon-germanium material (e.g., SiGeB). In this case, the germanium (Ge) concentration in the epitaxial layer 945 may range from approximately 30% germanium to approximately 55% germanium. The boron doping concentration may be approximately 5 x 10⁻⁶ per cubic centimeter. 20 From one atom to approximately 3 x 10^6 atoms per cubic centimeter. 21 Within the range of atoms. However, other combinations of the thickness, material, dopants, and doping concentration range of the epitaxial layer 945 are also within the scope of this disclosure. Figure 9E shows an isometric view of an exemplary portion of region 905 after the formation of source / drain region 225, which includes gate electrode layer 710 and spacer layer 720. Source / drain region 225 includes epitaxial layer 935 (e.g., a first epitaxial layer including a portion 935a and a convex portion 935b), epitaxial layer 940 (e.g., a second epitaxial layer), and epitaxial layer 945 (e.g., a third epitaxial layer). Furthermore, Figure 9E shows a capping layer 950 deposited over the epitaxial layer 945. The capping layer 950 protects the epitaxial layer 945 during the subsequent formation of the metal contact structure. The capping layer 950 can include a thickness ranging from approximately 5 nanometers to approximately 15 nanometers. In some embodiments, the capping layer 950 comprises a boron-doped silicon-germanium material (e.g., SiGeB). In this case, the germanium (Ge) concentration in the capping layer 950 can range from approximately 15% germanium to approximately 40% germanium. The boron doping concentration can be approximately 1 x 10⁻⁶ per cubic centimeter. 21 From one atom to approximately 2 x 10^6 atoms per cubic centimeter. 21 Within the range of atoms. However, other combinations of the thickness, material, dopant, and doping concentration range of the capping layer 950 are also within the scope of this disclosure. As shown in Figure 9E, the end of the first layer 310 (e.g., a sacrificial layer) includes an inner spacer 245, and the convex portion 935b is located within the concave region 925 at the end of the second layer 315 (e.g., a channel layer). After the source / drain region 225 is formed, the distance D5 (e.g., the proximity of the source / drain region 225 to the subsequently formed gate structure 240) can range from approximately 3 nanometers to approximately 6 nanometers. A distance D5 less than approximately 3 nanometers may correspond to an over-etched concave region 925, and a portion of the gate structure 240 may protrude into the channel layer (e.g., second layer 315) of the nanostructured transistor. A distance D5 greater than approximately 6 nanometers may correspond to an under-etched concave region 925, and the concave region 925 may have insufficient surface area for a seed layer (e.g., seed layer 930) to facilitate the growth of the epitaxial layer 935 (and may introduce pores in the epitaxial layer 935). Furthermore, this may increase the channel resistance (R0). ch This can reduce the performance of nanostructured transistors. However, other values ​​and ranges of distance D5 (e.g., proximity) are also within the scope of this disclosure. As shown in cross sections AA and BB of Figure 9F, the source / drain recess 805 is filled with one or more layers to form a source / drain region 225 within the source / drain recess 805. Region 905, including the source / drain region 225, further shows the source / drain region 225 extending into a trimmed region of the nanostructure channel 220 (e.g., second layer 315). The number and arrangement of devices shown in Figures 9A to 9F are provided as one or more examples. In reality, there may be additional materials, different materials, different arrangements of materials, different doping concentrations, or different size characteristics compared to those shown in Figures 9A to 9F. Figures 10A through 10D are diagrams of an exemplary embodiment 1000 of the alternative gate (RPG) process described herein. Exemplary embodiment 1000 includes an example of an alternative gate process for replacing a dummy gate structure 705 with a gate structure 240 (e.g., an alternative gate structure) of a semiconductor device 200. Figures 10A through 10D are shown from a plurality of perspective views shown in Figure 7A, and include a perspective view of section AA in Figure 7A, a perspective view of section BB in Figure 7A, and a perspective view of section CC in Figure 7A. In some embodiments, the operations described in conjunction with exemplary embodiment 900 are performed after the operations described in conjunction with Figures 3A, 3B, 4A, 4B, 5A through 5C, 6A through 6C, 7A and 7B, 8A through 8D, and 9A through 9F. As shown in cross-sections AA and BB of Figure 10A, an interlayer dielectric layer 250 is formed above the source / drain regions 225. The interlayer dielectric layer 250 fills the regions between the dummy gate structures 705, between the hybrid fin structures 620, and above the source / drain regions 225. The interlayer dielectric layer 250 is formed to reduce and / or prevent the possibility of damage to the source / drain regions 225 during the alternative gate process. The interlayer dielectric layer 250 may be referred to as an interlayer dielectric (ILD) zero (ILD0) layer or another ILD layer. In some embodiments, before forming the interlayer dielectric layer 250, a contact etch stop layer (CESL) is conformally deposited (e.g., using deposition tool 102) over the source / drain region 225, over the dummy gate structure 705, and over the spacer layer 720. Then, the interlayer dielectric layer 250 is formed on the CESL. The CESL can provide a mechanism to stop the etching process when forming contacts or vias in the source / drain region 225. The CESL can be formed of a dielectric material having a different etch selectivity than adjacent layers or components. The CESL can include or may be a nitrogen-containing material, a silicon-containing material, and / or a carbon-containing material. Furthermore, the CESL can include or may be silicon nitride (Si). x N y Silicon carbonitride (SiCN), carbon nitride (CN), silicon oxynitride (SiON), silicon oxycarbonate (SiCO), or combinations thereof, etc. CESL can be deposited using deposition processes such as ALD, CVD, or other deposition technologies. As shown in cross-sections BB and CC of Figure 10B, a gate replacement operation (e.g., by one or more of semiconductor process tools 102-112) is performed to remove the dummy gate structure 705 from the semiconductor device 200. Removing the dummy gate structure 705 leaves openings (or recesses) between the interlayer dielectric layers 250 above the source / drain regions 225 and between the hybrid fin structures 620. The dummy gate structure 705 can be removed in one or more etching operations. Such etching operations may include plasma etching, wet chemical etching, and / or other types of etching techniques. As shown in cross-sections BB and CC of Figure 10C, a nanostructure release operation (e.g., a SiGe release operation) is performed to remove the first layer 310 (e.g., a silicon-germanium layer). This results in an opening 1005 between nanostructure channels 220 (e.g., in the region surrounding nanostructure channels 220). The nanostructure release operation may include an etching tool 108 performing an etching operation based on differences in etch selectivity between the material of the first layer 310 and the material of the nanostructure channels 220, and between the material of the first layer 310 and the material of the inner spacer 245, to remove the first layer 310. In the etching operation, the inner spacer 245 may serve as an etch stop layer to protect the source / drain region 225 from etching. As further shown in Figure 10C, the covering sidewall 510 is removed during the nanostructure release operation. This provides access to the region surrounding the nanostructure channel 220, which allows alternative gate structures (e.g., gate structure 240) to be formed entirely around the nanostructure channel 220. As shown in cross-sections BB and CC of Figure 10D, the alternative gate operation continues, wherein deposition tool 102 and / or plating tool 112 form a gate structure (e.g., an alternative gate structure) 240 in an opening 1005 between the source / drain regions 225 and between the hybrid fin structure 620. Specifically, the gate structure 240 fills the regions between and around the nanostructure channels 220, which were previously occupied by the first layer 310 and the covering sidewalls 510, such that the gate structure 240 completely wraps around and surrounds the nanostructure channels 220. The gate structure 240 may include a metallic gate structure. Prior to forming the gate structure 240, a conformal high-k dielectric liner 1010 may be deposited on the nanostructure channels 220 and the sidewalls. The gate structure 240 may include additional layers, such as an interfacial layer, a work function tuning layer, and / or a metal electrode structure, etc. As described in conjunction with Figures 11A and 11B, the technique for forming part 1020 of the nanostructure channel 220 and the gate structure 240 can vary depending on the type of device (e.g., a PMOS device and an NMOS device, etc.). As further shown in section CC of Figure 10D, the cladding layer 505 is removed from the top of the STI region 215 to prevent the cladding sidewall layer from including leads below the hybrid fin structure 620 between adjacent fin structures 345, allowing the gate structure 240 to be formed such that the gate structure 240 does not include leads below the hybrid fin structure 620. In other words, since the gate structure 240 is formed in the region previously occupied by the cladding sidewall, the absence of leads below the hybrid fin structure 620 for the cladding sidewall also results in the absence of leads below the hybrid fin structure 620 of the gate structure 240. This reduces and / or prevents short circuits between the source / drain regions 225 below the gate structure 240 and the hybrid fin structure 620. As described above, the number and arrangement of forming operations and apparatus shown in Figures 10A to 10D are provided as one or more examples. In reality, compared with the forming operations and apparatus shown in Figures 10A to 10D, there may be additional forming operations and apparatus, fewer forming operations and apparatus, different forming operations and apparatus, or different arrangements of forming operations and apparatus. Figures 11A and 11B are diagrams of the exemplary nanostructured transistors described herein. Figures 11A and 11B are shown as perspective views from the cross-section BB shown in Figure 7A. In some embodiments, the exemplary nanostructured transistor is formed after incorporating the operations described in Figures 3A, 3B, 4A, 4B, 5A to 5C, 6A to 6C, 7A and 7B, 8A to 8D, 9A to 9F, and 10A to 10D. As shown in Figure 11A, a portion 1020 of the nanostructure transistor includes a nanostructure channel 220 above a plateau region 210 (e.g., the plateau region 210 of the fin structure 345 on the semiconductor substrate 205). The nanostructure channel 220 (e.g., formed during the RPG process by replacing the second layer 315) includes a concave region 925. Figure 11A further shows portions 240a and 240b of the gate structure 240. An inner spacer 245 is located at the end of the portion 240b. As shown in Figure 11A, buffer region 230 includes epitaxial layer 915. Source / drain region 225 includes epitaxial layer 935, which includes a portion 935a and a convex portion 935b extending into concave region 925. Source / drain region 225 also includes epitaxial layer 940 and epitaxial layer 945. A capping layer 235 is located above the source / drain region 225. A source / drain contact 1105 (referred to as MD) is formed to penetrate the ILD layer 250 to the source / drain region 225. To form the source / drain contact 1105, a recess is formed through the interlayer dielectric layer 250 and to reach the source / drain region 225. In some embodiments, the recess is formed in a portion of the source / drain region 225, such that the source / drain contact 1105 extends into a portion of the source / drain region 225. Figure 11B compares examples of a portion 1020 of different types of nanostructured transistors. Example 1110 on the left side of Figure 11B corresponds to a PMOS nanostructured transistor, and example 1115 on the right side of Figure 11B corresponds to an NMOS nanostructured transistor. In some embodiments, example 1110 is formed along a first axis perpendicular to the semiconductor substrate 205, and example 1115 is formed along a second axis perpendicular to the semiconductor substrate 205. As shown in the figure, Example 1110 includes a plurality of nanostructured channels 220c (e.g., a portion 240c2 of the gate structure is also shown) alternating with a portion 240c1 of the gate structure 240. Inner spacers 245c are located at the ends of said portions 240c1. Example 1110, which can be formed using the operations described in conjunction with Figures 9C through 9F, includes a convex portion 935c extending into the concave region 925. Based on the dimensional characteristics of the convex portion 935c and / or the concave region 925, the proximity D17 of Example 1110 (e.g., the distance from the source / drain region 225 to the gate structure 240 of the final semiconductor device 200) can include a range of approximately 3 nanometers to approximately 6 nanometers. However, other values ​​and ranges of proximity are also within the scope of this disclosure. Example 1110 further illustrates the spacer layer 720c. During the formation of the nanostructured transistor, the width D18 of the spacer layer 720c can be increased by up to 20% to increase the proximity D17. As shown in the figure, Example 1115 includes a plurality of nanostructured channels 220d alternating with portions 240d1 of the gate structure 240 (e.g., a portion 240d2 of the gate structure is also shown). Inner spacers 245d are located at the ends of said portions 240d1. During the formation of the concave region 925 in Example 1110, the source / drain recess (e.g., source / drain recess 805) in Example 1115 may have been masked by photoresist material. Therefore, no concave region 925 is formed at the end of the nanostructure channel 220d. Furthermore, the convex portion 935d extends from the end of the nanostructure channel 220d. Based on the absence of the concave region 925, the proximity D19 of Example 1115 (e.g., the distance from the source / drain region 225 to the gate structure 240 of the final semiconductor device 200) can be greater than the proximity D17 of Example 1110. For example, proximity D19 can include a range of approximately 5 nanometers to approximately 9 nanometers. However, other values ​​and ranges of proximity D19 are also within the scope of this disclosure. As described above, the operations and apparatus shown in Figures 11A and 11B are provided as one or more examples. In practice, compared with the operations and apparatus shown in Figures 11A and 11B, there may be additional operations to be performed and apparatus to be formed, fewer operations to be performed and apparatus to be formed, different operations to be performed and apparatus to be formed, or operations to be performed and apparatus to be formed in different arrangements. Figure 12 is a diagram 1200 comparing the formation of exemplary nanostructured transistors described herein. Diagram 1200 compares proximity 1205 during nanostructured transistor formation stage 1210. In some embodiments, the nanostructured transistor corresponds to the nanostructured transistor represented by Example 1110 of Figure 11B (e.g., a PMOS nanostructured transistor) and Example 1115 (e.g., an NMOS nanostructured transistor). Stage 1215 may correspond to the formation of a "pre-recess" stage (e.g., before the formation of the source / drain recess 805 and after the deposition of the spacer layer 720). At stage 1215, both the PMOS nanostructured transistor (e.g., corresponding to Example 1110) and the NMOS nanostructured transistor (e.g., corresponding to Example 1115) may have the same proximity 1220 (e.g., approximately 8 nanometers to approximately 10 nanometers, etc.). Stage 1225 may correspond to the formation of the "post-inner spacer" stage (e.g., after the formation of the inner spacer 245). At stage 1225, and due to the etching operation associated with the inner spacer 245, both the PMOS nanostructure transistor and the NMOS nanostructure transistor may have the same and reduced proximity 1230 (e.g., approximately 5 nm to approximately 9 nm, etc.). Stage 1235 can correspond to the "post-trimming" stage of formation (e.g., after trimming the second layer 315 included in the PMOS nanostructure transistor). At stage 1235, and because the second layer 315 included in the PMOS nanostructure transistor is etched (and the second layer 315 included in the NMOS nanostructure transistor is masked), differences in proximity may emerge. As shown at stage 1235, the proximity 1240 of the NMOS nanostructure transistor can remain relatively unchanged. However, the proximity 1250 of the PMOS nanostructure transistor can be further reduced (e.g., reduced to approximately 3 nm to approximately 6 nm, etc.). As described above, the operations and apparatus shown in Figure 12 are provided as one or more examples. In reality, compared to the operations and apparatus shown in Figure 12, there may be additional operations to be performed and apparatus to be formed, fewer operations to be performed and apparatus to be formed, different operations to be performed and apparatus to be formed, or operations to be performed and apparatus to be formed in different arrangements. Figure 13 is a diagram of exemplary components of one or more devices 1300 described herein. In some embodiments, one or more of the semiconductor process tools 102-112 and / or wafer / die transfer tools 114 may include one or more devices 1300 and / or one or more components of device 1300. As shown in Figure 13, device 1300 may include a bus 1310, a processor 1320, memory 1330, an input component 1340, an output component 1350, and a communication component 1360. Bus 1310 includes one or more components that enable wired and / or wireless communication between components in device 1300. Bus 1310 can couple two or more components of Figure 13 together, such as via operative coupling, communicative coupling, electronic coupling, and / or electrical coupling. Processor 1320 includes a central processing unit, graphics processing unit, microprocessor, controller, microcontroller, digital signal processor, field-programmable gate array, application-specific integrated circuit, and / or other types of processing components. Processor 1320 is implemented in hardware, firmware, or a combination of hardware and software. In some implementations, processor 1320 includes one or more processors and is programmed to perform one or more operations or processes described elsewhere herein. Memory 1330 includes volatile and / or nonvolatile memory. For example, memory 1330 may include random access memory (RAM), read-only memory (ROM), a hard disk drive, and / or other types of memory (e.g., flash memory, magnetic memory, and / or optical memory). Memory 1330 may include internal memory (e.g., RAM, ROM, or a hard disk drive) and / or removable memory (e.g., removable via a universal serial bus connection). Memory 1330 may be a non-transitory computer-readable medium. Memory 1330 stores information, instructions, and / or software (e.g., one or more software applications) related to the operation of device 1300. In some implementations, memory 1330 includes one or more memory modules, and the one or more memory modules are coupled to one or more processors (e.g., processor 1320) via bus 1310. Input component 1340 enables device 1300 to receive input, such as user input and / or sensed input. For example, input component 1340 may include a touch screen, keyboard, keypad, mouse, button, microphone, switch, sensor, global positioning system sensor, accelerometer, gyroscope, and / or actuator. Output component 1350 enables device 1300 to provide output, such as via display, speaker, and / or light-emitting diode. Communication component 1360 enables device 1300 to communicate with other devices via wired and / or wireless connections. For example, communication component 1360 may include a receiver, a transmitter, a transceiver, a modem, a network interface card, and / or an antenna. Device 1300 can perform one or more operations or processes described herein. For example, a non-transitory computer-readable medium (e.g., memory 1330) can store a set of instructions (e.g., one or more instructions or code) for execution by processor 1320. Processor 1320 can execute the set of instructions to perform one or more operations or processes described herein. In some embodiments, execution of the set of instructions by one or more processors 1320 causes one or more processors 1320 and / or device 1300 to perform one or more operations or processes described herein. In some embodiments, hardwired circuitry is used in place of or in combination with instructions to perform one or more operations or processes described herein. Additionally or alternatively, processor 1320 can be configured to perform one or more operations or processes described herein. Therefore, the embodiments described herein are not limited to any particular combination of hardware circuitry and software. The number and arrangement of components shown in Figure 13 are provided as an example. Compared to the components shown in Figure 13, device 1300 may include additional components, fewer components, different components, or components arranged differently. Additionally or alternatively, a set of components of device 1300 (e.g., one or more components) may perform one or more functions described as being performed by another set of components of device 1300. Figure 14 is a flowchart of an exemplary process 1400 related to a semiconductor device and its fabrication method. In some embodiments, one or more process blocks of Figure 14 may be performed by a combination of one or more semiconductor process tools (e.g., a combination of one or more semiconductor process tools 102-112). Alternatively or additionally, one or more process blocks of Figure 14 may be performed by one or more components in device 1300, such as processor 1320, memory 1330, input component 1340, output component 1350, and / or communication component 1360. As shown in Figure 14, process 1400 may include forming a plurality of nanostructure layers over the semiconductor substrate in a direction perpendicular to the semiconductor substrate (box 1410). For example, as described above, one or more of the semiconductor process tools 102-112, such as deposition tool 102, may perform one or more sequences of operations on the semiconductor substrate 205 to form a plurality of nanostructure layers in a direction perpendicular to the semiconductor substrate. In some embodiments, the plurality of nanostructure layers include a plurality of sacrificial layers (e.g., first layer 310) alternating with a plurality of channel layers (e.g., second layer 315). As further shown in Figure 14, process 1400 may include forming inner spacers at the ends of a plurality of sacrificial layers (block 1420). For example, as described above, one or more of semiconductor process tools 102-112, such as deposition tool 102, may perform a series of one or more operations to form inner spacers 245 at the ends of a plurality of sacrificial layers. As further shown in Figure 14, process 1400 may include forming concave regions at the ends of a plurality of channel layers (box 1430). For example, as described above, one or more of semiconductor process tools 102-112, such as etching tool 108, may perform one or more series of operations to form concave regions 925 at the ends of a plurality of channel layers. As further shown in Figure 14, process 1400 may include forming source / drain regions (box 1440) adjacent to the inner spacers and concave regions. For example, one or more of semiconductor process tools 102-112, such as deposition tool 102, may perform a series of operations to form source / drain regions 225 adjacent to the inner spacers 245 and concave regions 925. In some embodiments, forming the source / drain regions 225 includes a convex portion 935b of the epitaxial layer 935 forming the source / drain regions 225 within the concave regions 925 at the ends of a plurality of channel layers. As further shown in Figure 14, process 1400 may include forming a gate structure, and the gate structure includes a portion surrounding a plurality of channel layers (block 1450). For example, as described above, one or more of semiconductor process tools 102-112, such as deposition tool 102, exposure tool 104, development tool 106, and etching tool 108, may perform one or more series of operations to form a gate structure 240 including a portion surrounding a plurality of channel layers. Process 1400 may include additional implementations, such as any single implementation or any combination of one or more other processes described below and / or in conjunction with other content herein. In the first embodiment, process 1400 includes forming a buffer region 230 adjacent to the inner spacer 245 before forming the concave region 925 at the ends of the plurality of channel layers. In the second embodiment, forming the concave region 925 at the ends of the plurality of channel layers, alone or in combination with the first embodiment, includes the use of an etching operation. In some embodiments, the etching operation removes a portion of the buffer region 230. In the third embodiment, alone or in combination with one or more of the first and second embodiments, the etching operation includes a circulating flow of etchant to create concave regions 925a~925c with different depths D11, D12, D13 at the ends of the channel layer. In the fourth embodiment, alone or in combination with one or more of the first to third embodiments, process 1400 includes forming a seed layer 930 on the surface of the concave region before forming the source / drain region. While Figure 14 shows an example block for process 1400, in some implementations, process 1400 may include additional blocks, fewer blocks, different blocks, or blocks arranged differently compared to those depicted in Figure 14. Additionally or alternatively, two or more blocks in process 1400 may be executed in parallel. Figure 15 is a flowchart of an exemplary process 1500 related to a semiconductor device and its fabrication method. In some embodiments, one or more process blocks of Figure 15 may be performed by a combination of one or more semiconductor process tools (e.g., a combination of one or more semiconductor process tools 102-112). Alternatively or additionally, one or more process blocks of Figure 15 may be performed by one or more components in device 1300, such as processor 1320, memory 1330, input component 1340, output component 1350, and / or communication component 1360. As shown in Figure 15, process 1500 may include forming a first plurality of channel layers for n-type metal-oxide-semiconductor nanostructures and a second plurality of channel layers for p-type metal-oxide-semiconductor nanostructures on a semiconductor substrate (block 1510). For example, as described above, one or more of semiconductor process tools 102-112, such as deposition tool 102, may form a first plurality of channel layers (e.g., a first plurality of second layers 315) for n-type metal-oxide-semiconductor nanostructures and a second plurality of channel layers (e.g., a second plurality of second layers 315) for p-type metal-oxide-semiconductor nanostructures over semiconductor substrate 205. In some embodiments, forming the first plurality of channel layers includes forming the first plurality of channel layers along a first axis perpendicular to semiconductor substrate 205, and forming the second plurality of channel layers includes forming the second plurality of channel layers along a second axis perpendicular to semiconductor substrate 205. As further shown in Figure 15, process 1500 may include depositing mask material on the ends of the first plurality of channel layers (block 1520). For example, as described above, one or more of the semiconductor process tools 102-112, such as deposition tool 102 (e.g., a spin coating version of deposition tool 102) and exposure tool 104, may perform one or more series of operations to deposit mask material (e.g., photoresist material) on the ends of the first plurality of channel layers. As further shown in Figure 15, process 1500 may include removing a portion from the ends of the second plurality of channel layers to form concave regions at the ends of the second plurality of channel layers (block 1530). For example, one or more of semiconductor process tools 102-112, such as etching tool 108, may perform one or more series of operations to remove a portion from the ends of the second plurality of channel layers to form concave regions 925a-925c at the ends of the second plurality of channel layers. As further shown in Figure 15, process 1500 may include removing masking material after forming the concave region (box 1540). For example, as described above, one or more of the semiconductor process tools 102-112, such as etching tool 108 (e.g., plasma-based ashing agent), may perform one or more series of operations to remove masking material after forming the concave region. As further shown in Figure 15, process 1500 may include forming a first source / drain region adjacent to a first plurality of channel layers and a second source / drain region adjacent to a second plurality of channel layers (block 1550). For example, as described above, one or more of semiconductor process tools 102-112, such as deposition tool 102, may perform a series of operations to form a first source / drain region 225 adjacent to the first plurality of channel layers and a second source / drain region 225 adjacent to the second plurality of channel layers. In some embodiments, forming the first source / drain region 225 includes forming a first portion (convex portion) 935d of an epitaxial layer above the ends of the first plurality of channel layers. In some embodiments, forming the second source / drain region includes forming a second portion (convex portion) 935c of an epitaxial layer within a concave region at the ends of the second plurality of channel layers. As further shown in Figure 15, process 1500 may include forming a first gate structure and a second gate structure (block 1560). For example, as described above, one or more of semiconductor process tools 102-112, such as deposition tool 102, exposure tool 104, developing tool 106, and etching tool 108, may perform a sequence of one or more operations to form the first gate structure and the second gate structure. In some embodiments, forming the first gate structure includes forming a portion surrounding a first plurality of channel layers. In some embodiments, forming the second gate structure includes forming a portion surrounding a second plurality of channel layers. Process 1500 may include additional implementations, such as any single implementation or any combination of one or more other processes described below and / or in conjunction with other content herein. In the first embodiment, process 1500 includes performing a cleaning operation after removing the masking material and before forming the first source / drain region 225 and the second source / drain region 225. While Figure 15 shows an example block for process 1500, in some implementations, process 1500 may include additional blocks, fewer blocks, different blocks, or blocks arranged differently compared to those depicted in Figure 15. Additionally or alternatively, two or more blocks in process 1500 may be executed in parallel. Some embodiments described herein provide nanostructured transistors and methods for forming the same. The nanostructured transistor includes concave regions at the ends of a plurality of channel layers. The nanostructured transistor also includes convex portions of epitaxial material that comprise part of the source / drain regions of the nanostructured transistor and extend into the concave regions. The concave regions can be formed by performing masking, etching, and cleaning operations after depositing a buffer layer. This improves the performance of nanostructured transistors. For example, the channel length of a nanostructured transistor can be reduced to lower its channel resistance (Ro). ch Additionally or alternatively, the volume of the epitaxial material in the source / drain regions can be increased to reduce the parasitic resistance (Ro) of the nanostructured transistor. p R ch and / or R p This reduction can increase the drive current of nanostructured transistors. The concave ends of the channel layer can also reduce the likelihood of non-merging problems, thereby improving the yield of semiconductor devices including nanostructured channel transistors. As described in more detail above, some embodiments described herein provide a semiconductor device. The semiconductor device includes a plurality of channel layers over a semiconductor substrate, wherein the plurality of channel layers are arranged in a direction perpendicular to the semiconductor substrate, and wherein the plurality of channel layers include concave regions at the ends of the plurality of channel layers. The semiconductor device includes a gate structure surrounding each of the plurality of channel layers. The semiconductor device includes source / drain regions adjacent to the plurality of channel layers and the gate structure. In some embodiments, the source / drain region includes a layer of epitaxial material, wherein a convex portion of the epitaxial material layer extends into a concave region. In some embodiments, the thickness of the convex portion ranges from approximately 2 nanometers to approximately 5 nanometers. In some embodiments, the semiconductor device further includes a seed layer, which is situated between concave regions at the ends of a plurality of channel layers and convex portions of the epitaxial material layer extending into the concave regions. In some embodiments, the epitaxial material layers correspond to a first layer of a first epitaxial material, wherein the source / drain region further includes a second layer of a second epitaxial material above the first epitaxial material layer, and wherein the source / drain region further includes a third layer of a third epitaxial material above the second epitaxial material layer. In some embodiments, the proximity of the gate structure of the semiconductor device to the source / drain region ranges from approximately 3 nanometers to approximately 6 nanometers. In some embodiments, the semiconductor device further includes a buffer region below the source / drain region, wherein the buffer region comprises a layer of silicon material or silicon germanium material. In some embodiments, the thickness of the silicon material or silicon germanium material layer comprises a range of about 8 nanometers to about 40 nanometers. In some embodiments, the semiconductor device further includes inner spacers at the ends of a portion of the gate structure. In some embodiments, the ratio of the thickness of one or more concave regions to the thickness of one or more inner spacers comprises a range of about 1 to about 2. In some embodiments, the semiconductor device corresponds to a logic device or a static random access memory (SRAM) device. In some embodiments, the angle associated with one or more of the concave regions comprises a range of about 120 degrees to about 160 degrees. In some embodiments, a plurality of channel layers including the concave regions include a first channel layer and a second channel layer. The first channel layer includes a first concave region, wherein the first concave region includes a first depth. The second channel layer is below the first channel layer and includes a second concave region, wherein the second concave region includes a second depth that is greater than the first depth. As described in more detail above, some embodiments described herein provide a method for forming a semiconductor device. The method includes forming a plurality of nanostructure layers over a semiconductor substrate in a direction perpendicular to the semiconductor substrate, wherein the plurality of nanostructure layers include a plurality of sacrificial layers alternating with a plurality of channel layers. The method includes forming inner spacers at the ends of the plurality of sacrificial layers. The method includes forming concave regions at the ends of the plurality of channel layers. The method includes forming source / drain regions adjacent to the inner spacers and concave regions, wherein forming the source / drain regions includes a convex portion of the epitaxial layer forming the source / drain regions within the concave regions at the ends of the plurality of channel layers. The method includes forming a gate structure, and the gate structure includes surrounding a portion of the plurality of channel layers. In some embodiments, the formation method further includes forming a buffer region adjacent to the inner spacers before forming the concave region at the ends of the plurality of channel layers. In some embodiments, forming the concave region at the ends of the plurality of channel layers includes using an etching operation, wherein the etching operation removes a portion of the buffer region. In some embodiments, the etching operation includes a cyclic flow of etchant to create concave regions of different depths at the ends of the plurality of channel layers. In some embodiments, the formation method further includes forming a seed layer on the surface of the concave region before forming the source / drain regions. As described in more detail above, some embodiments described herein provide a method for forming a semiconductor device. The method includes forming a first plurality of channel layers for an n-type metal-oxide-semiconductor nanostructure transistor and a second plurality of channel layers for a p-type metal-oxide-semiconductor nanostructure transistor over a semiconductor substrate. Forming the first plurality of channel layers includes forming the first plurality of channel layers along a first axis perpendicular to the semiconductor substrate, and forming the second plurality of channel layers includes forming the second plurality of channel layers along a second axis perpendicular to the semiconductor substrate. The method includes depositing a masking material over the ends of the first plurality of channel layers. The method includes removing a portion from the ends of the second plurality of channel layers to form a concave region at the ends of the second plurality of channel layers. The method includes removing the masking material after forming the concave region. The formation method includes forming a first source / drain region adjacent to a first plurality of channel layers and a second source / drain region adjacent to a second plurality of channel layers, wherein forming the first source / drain region includes forming a first portion of an epitaxial layer above the ends of the first plurality of channel layers, and wherein forming the second source / drain region includes forming a second portion of an epitaxial layer in a concave region at the ends of the second plurality of channel layers. The formation method also includes forming a first gate structure and a second gate structure, wherein forming the first gate structure includes forming a portion surrounding the first plurality of channel layers, and wherein forming the second gate structure includes forming a portion surrounding the second plurality of channel layers. In some embodiments, the forming method further includes performing a cleaning operation after removing the masking material and before forming the first source / drain region and the second source / drain region. As used in this article, depending on the context, "satisfying a threshold" can refer to a value that is greater than, greater than or equal to, less than, less than or equal to, equal to, not equal to, or similar to the threshold. The foregoing disclosure outlines components of several embodiments, enabling those skilled in the art to better understand the nature of this disclosure. Those skilled in the art will understand that they can readily design or modify other processes and structures based on this disclosure to achieve the same objectives and / or advantages as the embodiments described herein. Those skilled in the art will also understand that these equivalent configurations do not depart from the spirit and scope of this disclosure, and that various changes, substitutions, or replacements can be made to this disclosure without departing from its spirit and scope. 100: Environment; 102, 104, 106, 108, 110, 112, 114: Tools; 200, 1300: Apparatus; 205: Semiconductor substrate; 210: Platform region; 215: Shallow trench isolation region; 220, 220d: Nanostructure channel; 225: Source / drain region; 230: Buffer region; 235, 325, 950: Capping layer; 240: Gate structure; 245, 245a, 245b: Inner spacer; 250: Interlayer dielectric layer; 300, 400, 500, 600, 700, 800, 900, 1000: Implementation method; 305: Stacked structure; 310, 3 10a, 310b: First layer; 315, 315a, 315b, 315c: Second layer; 320, 715: Hard masking layer; 330: Oxide layer; 335: Nitride layer; 240a, 240b, 240c1, 240c2, 240d1, 240d2; 340, 935a, 1020: Partial; 345, 345a, 345b: Fin structure; 405, 605: Liner; 410, 610: Dielectric layer; 505: Coating layer; 510: Coating sidewall; 615: High dielectric constant layer; 620: Hybrid fin structure; 705: Dummy gate structure; 710: Gate electrode layer; 720, 7 20c: Spacer layer; 725: Gate dielectric layer; 805: Source / drain recess; 810: Cavity; 815: Insulating layer; 905: Region; 910, 920, 1110, 1115: Examples; 915, 935, 940, 945: Epitaxial layers; 925, 925a, 925b, 925c: Concave regions; 930: Seed layers; 935b, 935c, 935d: Convex portions; 1005: Opening; 1010: Dielectric liner; 1105: Source / drain contact; 1200: Pattern; 1210, 1215, 1225, 1235: Stages; 1310: Bus; 1320: Processor 1 330: Memory; 1340: Input Component; 1350: Output Component; 1360: Communication Component; 1400, 1500: Process; 1410, 1420, 1430, 1440, 1450, 1510, 1520, 1530, 1540, 1550, 1560: Frame; D1, D3, D6, D7, D8, D9, D10, D16: Thickness; D2, D4: Height; D5: Distance; D11, D12, D13: Depth; D14, D15: Angle; D17, D19, 1205, 1220, 1230, 1240, 1250: Proximity; D18: Width. The best understanding of this disclosure can be achieved by reading the following detailed description in conjunction with the accompanying drawings. It should be noted that, according to industry standard practice, the various components are not necessarily drawn to scale. In fact, the dimensions of various components may be arbitrarily enlarged or reduced for clarity. Figure 1 is an example environment diagram in which the system and / or methods described herein can be implemented. Figure 2 is an example semiconductor device diagram described herein. Figures 3A and 3B are diagrams of an example embodiment of the fin formation process described herein. Figures 4A and 4B are diagrams of an example embodiment of the shallow trench isolation (STI) process described herein. Figures 5A through 5C are diagrams of an example embodiment of the cladding sidewall formation process described herein. Figures 6A through 6C are diagrams of an example embodiment of the hybrid fin structure formation process described herein. Figures 7A and 7B are diagrams of an example dummy gate structure formation process described herein. Figures 8A to 8D are diagrams illustrating exemplary embodiments of the source / drain recess formation process and the internal spacer formation process described herein. Figures 9A to 9F are diagrams illustrating exemplary embodiments of the source / drain region formation process described herein. Figures 10A to 10D are diagrams illustrating exemplary embodiments of the replacement gate process described herein. Figures 11A and 11B are diagrams illustrating exemplary nanostructure transistors described herein. Figure 12 is a diagram comparing the formation of exemplary nanostructure transistors described herein. Figure 13 is an exemplary assembly diagram of one or more devices described herein. Figures 14 and 15 are flowcharts of exemplary processes related to the formation of the semiconductor devices described herein. 245: Internal spacer 310: First Floor 315: Second Floor 710: Gate electrode layer 720: Spacer layer 900: Implementation Method 905: Area 925: Concave area D5: Distance

Claims

1. A semiconductor device, comprising: A plurality of channel layers are arranged above a semiconductor substrate, wherein the plurality of channel layers are arranged in a direction perpendicular to the semiconductor substrate, and wherein the plurality of channel layers include a concave region at one end of the plurality of channel layers; a gate structure surrounds each of the plurality of channel layers; and a source / drain region adjacent to the plurality of channel layers and the gate structure, wherein the source / drain region includes a layer of epitaxial material, wherein a convex portion of the epitaxial material layer extends into the concave region, and a thickness of the convex portion is in the range of about 2 nanometers to about 5 nanometers.

2. The semiconductor device as claimed in claim 1, further comprising: A crystalline layer, situated between a concave region at the end of the plurality of channel layers and a convex portion of the layer of epitaxial material extending into the concave region.

3. The semiconductor device as claimed in claim 1, wherein the layer of the epitaxial material corresponds to a first layer of a first epitaxial material, and wherein, The source / drain region further includes a second layer of a second epitaxial material above the first layer of the first epitaxial material, and wherein the source / drain region further includes a third layer of a third epitaxial material above the second layer of the second epitaxial material.

4. The semiconductor device as claimed in claim 1, wherein the proximity of the gate structure of the semiconductor device to the source / drain region is in the range of about 3 nanometers to about 6 nanometers.

5. The semiconductor device as claimed in claim 1, further comprising: A buffer region is located below the source / drain region, wherein the buffer region comprises a layer of silicon material or silicon-germanium material.

6. The semiconductor device as claimed in claim 1, further comprising: An inner spacer is located at one end of a portion of the gate structure.

7. The semiconductor device of claim 1, wherein the plurality of channel layers including the concave region comprises: A first channel layer includes a first concave region, wherein the first concave region includes a first depth; and a second channel layer below the first channel layer includes a second concave region, wherein the second concave region includes a second depth greater than the first depth.

8. A method for forming a semiconductor device, comprising: A plurality of nanostructure layers are formed above a semiconductor substrate in a direction perpendicular to the semiconductor substrate, wherein the plurality of nanostructure layers include a plurality of sacrificial layers alternating with a plurality of channel layers; an inner spacer is formed on one end of the plurality of sacrificial layers; a concave region is formed in one end of the plurality of channel layers; a source / drain region is formed, and the source / drain region is adjacent to the inner spacer and the concave region, wherein the formation of the source / drain region includes a convex portion of an epitaxial layer forming the source / drain region in the concave region at the end of the plurality of channel layers, wherein a thickness of the convex portion is in the range of about 2 nanometers to about 5 nanometers; and a gate structure is formed, wherein the gate structure includes a portion surrounding the plurality of channel layers.

9. A method for forming a semiconductor device, comprising: Forming a first plurality of channel layers for an n-type metal-oxide-semiconductor nanostructure and a second plurality of channel layers for a p-type metal-oxide-semiconductor nanostructure over a semiconductor substrate, wherein forming the first plurality of channel layers includes forming the first plurality of channel layers along a first axis perpendicular to the semiconductor substrate, and wherein forming the second plurality of channel layers includes forming the second plurality of channel layers along a second axis perpendicular to the semiconductor substrate; depositing a masking material over one end of the first plurality of channel layers; removing a portion from one end of the second plurality of channel layers to form a concave region at that end of the second plurality of channel layers; removing the masking material after forming the concave region; forming a first source / drain region adjacent to the first plurality of channel layers and a second source / drain region adjacent to the second plurality of channel layers; The formation of the first source / drain region includes forming a first portion of an epitaxial layer above the end of the first plurality of channel layers, and the formation of the second source / drain region includes forming a second portion of the epitaxial layer in the concave region at the end of the second plurality of channel layers, wherein the thickness of the second portion of the epitaxial layer is in the range of about 2 nanometers to about 5 nanometers; and the formation of a first gate structure and a second gate structure, wherein forming the first gate structure includes forming a portion surrounding the first plurality of channel layers, and wherein forming the second gate structure includes forming a portion surrounding the second plurality of channel layers.

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