Patent Publication Number: US-2021175341-A1

Title: Fin-Like Field Effect Transistor Patterning Methods For Achieving Fin Width Uniformity

Description:
This is a divisional application of U.S. patent application Ser. No. 16/387,889, filed Apr. 18, 2019, which is a non-provisional application of and claims benefit of U.S. Provisional Patent Application Ser. No. 62/698,536, filed Jul. 16, 2018, the entire disclosures of which are incorporated herein by reference. 
     BACKGROUND 
     The semiconductor integrated circuit (IC) industry has experienced exponential growth. Technological advances in IC materials and design have produced generations of ICs, where each generation has smaller and more complex circuits than the previous generation. In the course of IC evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometry size (i.e., the smallest component (or line) that can be created using a fabrication process) has decreased. This scaling down process generally provides benefits by increasing production efficiency and lowering associated costs. 
     Such scaling down has also increased the complexity of processing and manufacturing ICs and, for these advances to be realized, similar developments in IC processing and manufacturing are needed. For example, as fin-like field effect transistor (FinFET) technologies progress towards smaller feature sizes (such as 32 nanometers, 28 nanometers, 20 nanometers, and below), FinFET patterning processes are significantly constrained by decreasing process margins. Accordingly, although existing fin patterning processes have been generally adequate for their intended purposes, they have not been entirely satisfactory in all respects 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure is best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale and are used for illustration purposes only. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion. 
         FIG. 1  is a flow chart of a method for fabricating a fin-like field effect transistor (FinFET) device according to various aspects of the present disclosure. 
         FIGS. 2A-2P  are fragmentary diagrammatic views of a FinFET device, in portion or entirety, at various fabrication stages, such as those associated with the method of  FIG. 1 , according to various aspects of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The following disclosure provides many different embodiments, or examples, for implementing different features of the invention. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. 
     In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. Moreover, the formation of a feature on, connected to, and/or coupled to another feature in the present disclosure that follows may include embodiments in which the features are formed in direct contact, and may also include embodiments in which additional features may be formed interposing the features, such that the features may not be in direct contact. In addition, spatially relative terms, for example, “lower,” “upper,” “horizontal,” “vertical,” “above,” “over,” “below,” “beneath,” “up,” “down,” “top,” “bottom,” etc. as well as derivatives thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) are used for ease of the present disclosure of one features relationship to another feature. The spatially relative terms are intended to cover different orientations of the device including the features. 
       FIG. 1  is a flow chart of a method  100  for fabricating an integrated circuit (IC) device according to various aspects of the present disclosure. In some implementations, the IC device includes a fin-like field effect transistor (FinFET) device, which generally refers to any fin-based transistor device, such as a fin-based, multi-gate transistor. At block  110 , method  100  includes forming a mandrel layer over a substrate. At block  120 , a first cut is performed to remove a portion of the mandrel layer, thereby leaving a mandrel feature and a dummy mandrel feature disposed over the substrate. The dummy mandrel feature is disposed directly adjacent to the mandrel feature. At block  130 , method  100  proceeds with etching the substrate using the mandrel feature and the dummy mandrel feature as an etch mask, thereby forming a dummy fin feature and an active fin feature. The dummy fin feature is separated from the active fin feature by a first spacing along a first direction. At block  140 , a second cut is performed to remove a portion of the dummy fin feature and a portion of the active fin feature, thereby forming dummy fins separated by a second spacing and active fins separated by the second spacing. The second spacing is along a second direction that is substantially perpendicular to the first direction. At block  150 , a third cut is performed to remove the dummy fins, thereby forming fin openings. At block  160 , the fin openings are filled with a dielectric material, thereby forming dielectric fins. In some implementations, method  100  may continue to fabricate other features of the IC device. Additional steps can be provided before, during, and after method  100 , and some of the steps described can be moved, replaced, or eliminated for additional embodiments of method  100 . The discussion that follows illustrates FinFET devices that can be fabricated according to various embodiments of method  100 . 
       FIGS. 2A-2P  are fragmentary diagrammatic views of a FinFET device  200 , in portion or entirety, at various fabrication stages (such as those associated with method  100 ) according to various aspects of the present disclosure. FinFET device  200  may be included in a microprocessor, a memory, and/or other IC device. In some implementations, FinFET device  200  may be a portion of an IC chip, a system on chip (SoC), or portion thereof, that includes various passive and active microelectronic devices such as resistors, capacitors, inductors, diodes, metal-oxide semiconductor field effect transistors (MOSFETs), complementary metal-oxide semiconductor (CMOS) transistors, bipolar junction transistors (BJTs), laterally diffused MOS (LDMOS) transistors, high voltage transistors, high frequency transistors, other suitable components, or combinations thereof.  FIGS. 2A-2P  have been simplified for the sake of clarity to better understand the inventive concepts of the present disclosure. Additional features can be added in FinFET device  200 , and some of the features described below can be replaced, modified, or eliminated in other embodiments of FinFET device  200 . 
     In  FIGS. 2A-2D , a fin cut first process is performed to define active regions of FinFET device  200 . The fin cut first process implements a multiple patterning process, such as a double patterning lithography (DPL) process (for example, a lithography-etch-lithography-etch (LELE) process, a self-aligned double patterning (SADP) process, a spacer-is-dielectric patterning (SIDP) process, other double patterning process, or combinations thereof), a triple patterning process (for example, a lithography-etch-lithography-etch-lithography-etch (LELELE) process, a self-aligned triple patterning (SATP) process, other triple patterning process, or combinations thereof), other multiple patterning process (for example, self-aligned quadruple patterning (SAQP) process), or combinations thereof. Generally, multiple patterning processes combine lithography processes and self-aligned processes, allowing patterns to be created that have, for example, pitches smaller than what is otherwise obtainable using a single, direct lithography process. For example, in some implementations, a patterned sacrificial layer is formed over a substrate using a lithography process, and spacers are formed alongside the patterned sacrificial layer using, for example, a self-aligned process. Then, the patterned sacrificial layer is removed, and the spacers can be used to pattern an underlying layer. In some implementations, directed self-assembly (DSA) techniques are implemented during the multiple patterning processes. The present disclosure contemplates variations to the fin cut first process described below and notes that various steps may be omitted for ease of discussion. 
     Turning to  FIG. 2A , FinFET device  200  includes a substrate (wafer)  205 . In the depicted embodiment, substrate  205  is a bulk substrate that includes silicon. Alternatively, in some implementations, substrate  205  includes a bulk substrate (including, for example, silicon) and one or more material layers disposed over the bulk substrate. For example, the one or more material layers can include a semiconductor layer stack having various semiconductor layers (such as a heterostructure) disposed over the bulk substrate, where the semiconductor layer stack is subsequently patterned to form fins. The semiconductor layers can include any suitable semiconductor materials, such as silicon, germanium, silicon germanium, other suitable semiconductor materials, or combinations thereof. The semiconductor layers can include same or different materials, etching rates, constituent atomic percentages, constituent weight percentages, thicknesses, and/or configurations depending on design requirements of FinFET device  200 . In some implementations, the semiconductor layer stack includes alternating semiconductor layers, such as semiconductor layers composed of a first material and semiconductor layers composed of a second material. For example, the semiconductor layer stack alternates silicon layers and silicon germanium layers (for example, Si/SiGe/Si from bottom to top). In some implementations, the semiconductor layer stack includes semiconductor layers of the same material but with alternating constituent atomic percentages, such as semiconductor layers having a constituent of a first atomic percent and semiconductor layers having the constituent of a second atomic percent. For example, the semiconductor layer stack includes silicon germanium layers having alternating silicon and/or germanium atomic percentages (for example, Si a Ge b /Si c Ged/Si a Ge b  from bottom to top, where a, c are different 0  atomic percentages of silicon and b, d are different atomic percentages of germanium). Alternatively or additionally, the bulk substrate and/or the one or more material layers include another elementary semiconductor, such as germanium; a compound semiconductor, such as silicon carbide, silicon phosphide, gallium arsenide, gallium phosphide, indium phosphide, indium arsenide, indium antimonide, zinc oxide, zinc selenide, zinc sulfide, zinc telluride, cadmium selenide, cadnium sulfide, and/or cadmium telluride; an alloy semiconductor, such as SiGe, SiPC, GaAsP, AlInAs, AlGaAs, GalnAs, GaInP, and/or GaInAsP; other group III-V materials; other group II-V materials; or combinations thereof. Alternatively, substrate  205  is a semiconductor-on-insulator substrate, such as a silicon-on-insulator (SOI) substrate, a silicon germanium-on-insulator (SGOI) substrate, or a germanium-on-insulator (GOI) substrate. Semiconductor-on-insulator substrates can be fabricated using separation by implantation of oxygen (SIMOX), wafer bonding, and/or other suitable methods. 
     A patterning layer  210  is disposed over substrate  205 . Patterning layer  210  includes a material that is different than a material of substrate  205  to achieve etching selectivity during a fin etching process, such that substrate  205  can be selectively etched with minimal (or no) etching of patterning layer  210 , and vice versa. In the depicted embodiment, patterning layer  210  includes a pad layer  212  and a mask layer  214 , where pad layer  212  is disposed on substrate  205  and mask layer  214  is disposed on pad layer  212 . In some implementations, pad layer  212  includes silicon and oxygen (for example, silicon oxide), and mask layer  214  includes silicon and nitrogen (for example, silicon nitride or silicon oxynitride). In some implementations, pad layer  212  is a silicon oxide layer formed by thermal oxidation and/or other suitable process, and mask layer  214  is a silicon nitride layer formed by chemical vapor deposition (CVD), low pressure CVD (LPCVD), plasma enhanced CVD (PECVD), thermal nitridation (for example, of silicon), other suitable process, or combinations thereof. In some implementations, pad layer  212  includes a material that promotes adhesion between substrate  205  and mask layer  214  and/or functions as an etch stop layer when etching mask layer  214 . Other materials for and/or methods for forming pad layer  212  and/or mask layer  214 , along with other configurations of patterning layer  210 , are contemplated by the present disclosure. 
     Turning to  FIG. 2B , a mandrel layer  220  is formed over patterning layer  210 . Mandrel layer  220  includes an array of mandrels disposed on patterning layer  220 , where adjacent mandrels are separated by spacing S. In the depicted embodiment, mandrel layer  220  includes mandrels  222 A, which correspond with active fins to be formed in a portion of substrate  205 , and dummy mandrels  222 B, which correspond with extra mandrel features that are included within mandrel layer  220  to maintain mandrel feature density (and thus minimize patterning effects, such as fin etch loading effects, that can affect uniformity) and/or correspond with dielectric fins to be formed in a portion of substrate  205 , where the dielectric fins are electrically non-functional features of FinFET device  200 . In some implementations, widths of mandrels  222 A are substantially equal to desired widths (also referred to as critical dimensions (CDs)) of fins of FinFET device  200 . In some implementations, widths of mandrels  222 A are greater than the desired widths of fins of FinFET device  200  to compensate for consumption of the fins and/or patterning layers used to form the fins during subsequent processing (for example, to compensate for etch loading effects). Mandrel layer  220  includes a material that is different than patterning layer  210  (in particular, mask layer  214 ) to achieve etching selectivity during an etching process, such that patterning layer  210  can be selectively etched with minimal (or no) etching of mandrel layer  220 , and vice versa. Mandrel layer  220  includes a semiconductor material and/or a dielectric material that achieves desired etching selectivity, such as silicon, amorphous silicon, silicon oxide, silicon nitride, silicon oxynitride, silicon carbide, other suitable material, or combinations thereof. 
     In the depicted embodiment, mandrel layer  220  is formed using a spacer patterning technique. For example, forming mandrel layer  220  includes forming a patterned sacrificial layer (which includes sacrificial features having a first spacing) over patterning layer  210  using a lithography process, forming a spacer layer over the patterned sacrificial layer, etching the spacer layer to form spacers along sidewalls of each sacrificial feature (for example, the spacer layer is removed from a top surface of the sacrificial features and a portion of a top surface of patterning layer  210 ), and removing the patterned sacrificial layer, leaving spacers having a second spacing (which can be referred to as a patterned spacer layer, which includes openings that expose a portion of patterning layer  210 ). Mandrel layer  220  and mandrels  222 A,  222 B can thus respectively be referred to as a spacer layer and spacers. In some implementations, the spacer layer is conformally formed over the patterned sacrificial layer, such that the spacer layer has a substantially uniform thickness. In some implementations, the spacers are trimmed before or after removing the patterned sacrificial layer. Alternatively, in some implementations, mandrel layer  220  is formed by forming a mandrel material layer (including, for example, a dielectric material), forming a patterned resist layer over the mandrel material layer using a lithography process, etching the mandrel material layer using the patterned resist layer as an etch mask, and removing the patterned resist layer (for example, by a resist stripping process), leaving a patterned mandrel material layer that includes openings that expose patterning layer  110 . Alternatively, in some implementations, mandrel layer  220  is a patterned resist layer, such that mandrel layer  220  includes a resist material. The lithography processes can include forming a resist layer (for example, by spin-on coating), performing a pre-exposure baking process, performing an exposure process using a mask, performing a post-exposure baking process, and performing a developing process. During the exposure process, the resist layer is exposed to radiation energy (such as ultraviolet (UV) light, deep UV (DUV) light, or extreme UV (EUV) light), where the mask blocks, transmits, and/or reflects radiation to the resist layer depending on a mask pattern of the mask and/or mask type (for example, binary mask, phase shift mask, or EUV mask), such that an image is projected onto the resist layer that corresponds with the mask pattern. Since the resist layer is sensitive to radiation energy, exposed portions of the resist layer chemically change, and exposed (or non-exposed) portions of the resist layer are dissolved during the developing process depending on characteristics of the resist layer and characteristics of a developing solution used in the developing process. After development, the patterned resist layer includes a resist pattern that corresponds with the mask. The patterned resist layer can then be used as an etch mask during an etching process to remove portions of an underlying layer, such as a sacrificial layer or a mandrel material layer. The etching process can include a dry etching process (for example, a reactive ion etching (RIE) process), a wet etching process, other suitable etching process, or combinations thereof. After the etching process, the patterned resist layer can be removed. Alternatively, the exposure process can implement maskless lithography, electron-beam writing, ion-beam writing and/or nanoprint technology. 
     Turning to  FIG. 2C , dummy mandrels  222 B of mandrel layer  220  are removed to define fin active regions of FinFET device  200 , such as a fin active region  224  and a fin active region  226 , thereby forming patterned mandrel layer  220 ′. In the depicted embodiment, fin active region  224  is directly adjacent to fin active region  226 , such that no other fin active region is disposed between fin active region  224  and fin active region  226 . Typically, the fin cut first process would continue by removing all dummy mandrels  222 B, such that only mandrels  222 A corresponding with active fins to be formed in substrate  205  remain. However, it has been observed that density variations arising from such fin cut first techniques can result in etching effects that induce fin width (or fin CD) differences in active fins that can negatively affect FinFET device performance. For example, when dummy mandrels  222 B are completely removed from mandrel layer  220 , a spacing S 2  is defined between mandrels  222 A in directly adjacent fin active regions, which results in areas surrounding each mandrel  222 A having different densities. The different densities can result in fin active region  224  and fin active region  226  having an isolated (iso) mandrel and a dense mandrel, where left/right spacing of the iso mandrel is greater than left/right spacing of the dense mandrel. Left/right spacing (loading) generally refers to a sum of a spacing between a left sidewall of a mandrel and a closest device feature (for example, another mandrel or an edge of substrate  205 ) along a width direction (here, the x-direction) of the mandrel and a spacing between a right sidewall of the mandrel and a closest device feature along the width direction. In other words, L/R loading=L spacing+R spacing. In some implementations, a threshold left/right loading is defined for classifying a mandrel as an iso mandrel or a dense mandrel. For purposes of the present example, it is assumed that the left/right loading corresponding with outermost mandrels  222 A is less than the threshold left/right loading, such that the outermost mandrels  222 A are classified as dense mandrels and innermost mandrels  222 A are classified as iso mandrels ( FIG. 2C ). 
     Since left/right loading of mandrels  222 A is subsequently transferred to active fins (when mandrels  222 A are used as an etch mask to form the active fins), an area of substrate  205  that corresponds with iso mandrels may etch differently (for example, more quickly or more slowly in one or more directions depending on whether the etching is configured anisotropically or isotropically) than an area of substrate  205  that corresponds with dense mandrels, such that widths of active fins corresponding with iso mandrels are different than widths of active fins corresponding with dense mandrels. Such etching differences resulting from left/right loading are often referred to as fin etch iso/dense loading. In some implementations, it has been observed that an area of substrate  205  that corresponds with iso mandrels etches more slowly than an area of substrate  205  that corresponds with dense mandrels, such that widths of active fins corresponding with iso mandrels (referred to as iso fins) are greater than widths of active fins corresponding with dense mandrels (referred to as dense fins). Such fin etch iso/dense loading has led to less control of short channel effects in iso fins compared to dense fins (for example, increases in drain induced barrier lowering (DIBL)), degrading FinFET device performance and/or resulting in undesired variations in FinFET device performance. Further, as IC technology nodes continue to decrease, these issues are exacerbated by ever-shrinking gate lengths in FinFET devices fabricated at the advanced IC technology nodes. 
     The present disclosure proposes inserting dummy fins adjacent to isolated active fins, such as edge fins of a FinFET device, to reduce left/right loading of isolated active fins. Density in an area of isolated active fins is thus closer (and, in some implementations, equivalent) to density in an area of dense active fins, thereby reducing fin etch iso/dense loading and improving fin width uniformity. For example, in  FIG. 2C , the fin cut first process removes a subset of dummy mandrels  222 B′ (instead of all of dummy mandrels  222 B), such that fin region  224  and fin region  226  each have one of dummy mandrels  222 B disposed adjacent to mandrels  222 A that are classified as iso mandrels. In the depicted embodiment, remaining dummy mandrels  222 B are disposed directly adjacent to mandrels  222 A, thereby defining a spacing S 3  between dummy mandrels  222 B in fin active region  224  and fin active region  226  that is less than spacing S 2 . Remaining dummy mandrels  222 B reduce left/right loading of innermost mandrels  222 A (for example, from S+S 2  to S+S). In some implementations, left/right loading of innermost mandrels  222 A is substantially equal to left/right loading of outermost mandrels  222 A. For example, left/right loading of innermost mandrels  222 A and outermost mandrels  222 A is S+S. The present disclosure contemplates any subset of dummy mandrels removed, so long as remaining dummy mandrels reduce left/right loading of isolated mandrels, such as innermost mandrels  222 A, to less than or equal to a threshold left/right loading. In some implementations, when spacing between mandrels of fin active regions, such as spacing S 2 , is greater than or equal to a threshold spacing (for example, defining a spacing that has been determined to result in unacceptable levels of fin etch iso/dense loading), the fin cut first process leaves at least one dummy mandrel in each fin active region to define a spacing, such as spacing S 3 , between dummy fins of the fin active regions. In such implementations, when spacing between mandrels of fin active regions is less than the threshold spacing, all dummy mandrels are removed between mandrels defining the fin active regions. 
     Removing subset of dummy mandrels  222 B′ includes forming a patterned masking layer over mandrel layer  220  that includes a cut pattern defining protected mandrels (here, mandrels  222 A and at least one dummy mandrel  222 B disposed adjacent to each mandrel  222 A classified as an iso mandrel) and unprotected (unwanted) mandrels (here, subset of dummy mandrels  222 B′) and etching the unprotected mandrels using the patterned masking layer as an etch mask. In some implementations, the cut pattern defines an opening in the patterned masking layer that exposes the unprotected mandrels. In some implementations, the patterned masking layer is a patterned resist layer formed by a lithography process, such as those described herein. In some implementations, the patterned masking layer is a patterned hard mask layer, which is formed by depositing a hard mask layer over mandrel layer  220 , forming a patterned resist layer having the cut pattern using a lithography process, such as those described herein, and etching the hard mask layer using the patterned resist layer as an etch mask, such that the patterned hard mask layer includes the cut pattern exposing the unprotected mandrels. In some implementations, the patterned masking layer has a multi-layer structure. In some implementations, subset of dummy mandrels  222 B′ is selectively etched without etching (or without significantly etching) the patterned masking layer. The etching process is a dry etching process, a wet etching process, or combinations thereof. Various etching parameters can be tuned to selectively etch subset of dummy mandrels  222 B′, such as etchant composition, etching temperature, etching solution concentration, etching time, etching pressure, source power, RF bias voltage, RF bias power, etchant flow rate, other suitable etching parameters, or combinations thereof. In some implementations, a wet etching process uses an etching solution that includes tetramethylammonium hydroxide (TMAH), hydrofluoric acid (HF), sulfuric acid (H 2 SO 4 ), hydrogen chloride (HC 1 ), ammonium hydroxide (NH 4 OH), hydrogen peroxide (H 202 ), other suitable wet etching constituent, or combinations thereof. Thereafter, the patterned masking layer is removed (for example, by a resist stripping process and/or a selective etching process), leaving mandrels  222 A and dummy mandrels  222 B as depicted in  FIG. 2C . 
     Turning to  FIG. 2D , a fin etching process is performed to define a fin structure  228 A and a fin structure  228 B (collectively referred to as a fin layer) in a portion of substrate  205  using mandrel layer  220 ′ as an etch mask. Fin structure  228 A is disposed in fin active region  224 , and fin structure  228 B is disposed in fin active region  226 . In the depicted embodiment, fin structure  228 A and fin structure  228 B each include two active fins  230 A and one dummy fin  232 B, where dummy fins  232 B are configured between active fins  230 A of adjacent fin structures  228 A,  228 B. Spacing of mandrel layer  220 ′ is transferred to the fin layer, such that fins of fin structures  228 A,  228 B are separated by spacing S and dummy fins  230 B of fin structures  228 A,  228 B are separated by spacing S 3 . Active fins  230 A and dummy fins  230 B are oriented substantially parallel to one another, each having a width defined in an x-direction, a length defined in a y-direction, and a height defined in a z-direction. Active fins  230 A and dummy fins  230 B have substantially the same widths, lengths, and heights. In the depicted embodiment, where substrate  205  is a bulk substrate that includes silicon, active fins  230 A and dummy fins  230 B include silicon. Alternatively, in some implementations, where substrate  205  includes a semiconductor layer stack disposed over a bulk substrate, active fins  230 A and dummy fins  230 B are defined in the semiconductor layer stack, such that active fins  230 A and dummy fins  230 B include one or more semiconductor material layers. In furtherance of the depicted embodiment, trenches  232 A are defined between fins of fin structures  228 A,  228 B, and a trench  232 B is defined between adjacent fin structures  228 A,  228 B (here, between dummy fin  230 B of fin structure  228 A and dummy fin  230 B of fin structure  228 B). Trenches  232 A,  232 B have sidewalls defined by sidewalls of active fins  230 A, dummy fins  230 B, and/or patterning layer  210  and bottoms defined by top surfaces of substrate  205 . 
     The fin etching process selectively etches patterning layer  210  and substrate  205  without etching (or without significantly etching) mandrel layer  220 ′, such that mandrels  222 A and dummy mandrels  222 B serve as an etch mask for removing portions of patterning layer  210  and substrate  205 . Inserting dummy fins  230 B (which correspond with remaining dummy mandrels  222 B) adjacent to innermost, isolated active fins  230 A (which correspond with innermost mandrels  222 A classified as iso mandrels) reduces fin etch iso/dense loading, such that widths of innermost active fins  230 A are substantially similar to widths of outermost active fins  220 B. In some implementations, an area of substrate  205  corresponding with innermost mandrels  222 A etches at about the same rate as an area of substrate  205  corresponding with outermost mandrels  222 A. In some implementations, fin etch iso/dense loading is reduced by as much as  45 % compared to fin etch iso/dense loading that arises during conventional fin cut first processes. The etching process is a dry etching process, a wet etching process, or combinations thereof. In some implementations, the fin etching process is an anisotropic dry etching process (for example, a RIE process) configured to substantially remove patterning layer  210  and a portion of substrate  205  along the y-direction without removal (or without significant removal) of patterning layer  210  and the portion of substrate  205  along the x-direction. In some implementations, a dry etching process uses a fluorine-containing precursor (for example, CF 4 , SF 6 , NF 3 , CH 2 F 2 , CHF 3 , and/or C 2 F 6 ), an oxygen-containing precursor, a chlorine-containing precursor (for example, C 12 , CHC 13 , CC 14 , and/or BC 13 ), a bromine-containing precursor (for example, HBr and/or CHBR 3 ), an iodine-containing precursor, other suitable precursor (which can be used to generate an etchant gas and/or etching plasma), or combinations thereof. In some implementations, a wet etching process implements an etching solution that includes TMAH, NH 4 OH, H 202 , H 2 SO 4 , HF, HC 1 , other suitable wet etching constituent, or combinations thereof. Various etching parameters can be tuned to selectively etch patterning layer  210  and substrate  205 , such as etchant composition, etching temperature, etching solution concentration, etching time, etching pressure, source power, RF bias voltage, RF bias power, etchant flow rate, other suitable etching parameters, or combinations thereof. The present disclosure contemplates any combination of etching processes and/or other processes for defining fin structure  228 A and fin structure  228 B. Mandrel layer  220 ′ can be removed (for example, by an etching process) after etching patterning layer  210  or substrate  205 . The etching process can selectively etch mandrels  222 A and dummy mandrels  222 B without etching (or without significantly etching) patterning layer  210  and/or substrate  205 . In some implementations, patterning layer  210  may be partially removed during the fin etching process. In some implementations, patterning layer  210  is omitted. In such implementations, mandrel layer  220  includes a material that is different than substrate  205  to achieve etching selectivity during an etching process, such that portions of substrate  205  can be selectively etched with minimal (or no) etching of mandrel layer  220 ′, and vice versa. In such implementations, mandrel layer  220 ′ can serves as an etch mask for patterning substrate  205 . 
     Turning to  FIG. 2E , an isolation layer  240  is formed over FinFET device  200 . Isolation layer  240  covers a top surface of substrate  205 , patterning layer  210 , active fins  230 A, and dummy fins  230 B. Isolation layer  240  also completely fills trenches  232 A and partially fills trench  232 B, though the present disclosure contemplates embodiments where isolation layer  240  partially fills trenches  232 A and/or completely fills trench  232 B. Isolation layer  240  is subsequently patterned (which is described in detail below) to form an isolation feature, such as a shallow trench isolation feature, that electrically isolates active fins  230 A from one another. Isolation layer  240  thus includes an isolation material, such as silicon oxide, silicon nitride, silicon oxynitride, other suitable isolation material (for example, including silicon, oxygen, nitrogen, carbon, and/or other suitable isolation constituent), or combinations thereof. In the depicted embodiment, isolation layer  240  includes an oxide material, such as silicon oxide, and can thus be referred to as an oxide layer. In some implementations, isolation layer  240  includes a multi-layer structure, such as a bulk dielectric layer disposed over a liner dielectric layer, where the bulk dielectric layer and the liner dielectric layer include materials depending on design requirements. In some implementations, isolation layer  240  includes a dielectric layer disposed over a doped liner layer (including, for example, boron silicate glass (BSG) or phosphosilicate glass (PSG)). Isolation layer  240  is deposited by CVD, physical vapor deposition (PVD), atomic layer deposition (ALD), high density plasma CVD (HDPCVD), metal organic CVD (MOCVD), remote plasma CVD (RPCVD), PECVD, LPCVD, atomic layer CVD (ALCVD), atmospheric pressure CVD (APCVD), other suitable deposition process, or combinations thereof. 
     Turning to  FIG. 2F , a fin end cut process is performed to remove a portion of active fins  230 A and a portion of dummy fins  230 B, thereby defining FinFET device regions of FinFET device  200 . In the depicted embodiment, the fin end cut process forms a trench  245  that divides fin active region  224  into a FinFET device region  250 A and a FinFET device region  250 B and fin active region  226  into a FinFET device region  250 C and a FinFET device region  250 D. Trench  245  has sidewalls defined end sidewalls of isolation layer  240 , active fins  230 A, dummy fins  230 B, and patterning layer  210  and a bottom defined by the top surface of substrate  205 . Each of FinFET device regions  250 A- 250 D includes two active fins  230 A and one dummy fin  230 B. Adjacent FinFET device regions  250 A- 250 D are separated by spacing S 3  defined between dummy fins  230 B along the x-direction, instead of spacing S 2  defined between active fins  230 A. For example, spacing S 3  separates FinFET device region  250 A and FinFET device region  250 C, and spacing S 3  separates FinFET device region  250 B and FinFET device region  250 D. Trench  245  creates an end-to-end spacing  252  between adjacent FinFET device regions along the y-direction. For example, ends of fins (often referred to as fin line ends) of FinFET device region  250 A and ends of fins of FinFET device region  250 B are separated by end-to-end spacing  252  and ends of fins of FinFET device region  250 C and ends of fins of FinFET device region  250 D are separated by end-to-end spacing  252 . 
     The fin end cut process includes depositing a masking layer over isolation layer  140  (in some implementations, the masking layer fills trenches  232 B); performing a lithography and etching process, such as those described herein, to define a cut pattern in the masking layer that exposes a portion of isolation layer  240 ; etching the exposed portion of isolation layer  240 , thereby exposing a portion of active fins  230 A and dummy fins  230 B underlying isolation layer  240 ; etching the exposed portion of active fins  230 A and dummy fins  230 B; and removing the masking layer, thereby forming trench  245 . The masking layer can be removed before or after etching the exposed portion of active fins  230 A and dummy fins  230 B. In some implementations, the masking layer is a resist layer. In some implementations, the masking layer is a hard mask layer, which is formed by depositing a hard mask layer over isolation layer  240  (in some implementations, the hard mask layer fills trenches  232 B), forming a patterned resist layer having the cut pattern using a lithography process, such as those described herein, and etching the hard mask layer using the patterned resist layer as an etch mask, such that the patterned hard mask layer includes the cut pattern. In some implementations, the masking layer has a multi-layer structure. In some implementations, the exposed portion of isolation layer  140  is selectively etched without etching (or without significantly etching) the masking layer and/or the portion of active fins  230 A and dummy fins  230 B underlying isolation layer  140 . In some implementations the exposed portion of active fins  230 A and dummy fins  230 B is selectively etched without etching (or without significantly etching) the masking layer and/or isolation layer  140 . In some implementations, an etching process is tuned throughout to etch silicon oxide without etching (or without significantly etching) silicon, and vice versa, to remove the exposed portions of isolation layer  140 , active fins  230 A, and dummy fins  230 B. In some implementations, a dry etching process uses a fluorine-containing precursor (for example, CF 4 , SF 6 , NF 3 , C 2 F 2 , CHF 3 , and/or C 2 F 6 ), an oxygen-containing precursor, a chlorine-containing precursor (for example, Cl 2 , CHCl 3 , CCl 4 , and/or BCl 3 ), a bromine-containing precursor (for example, HBr and/or CHBR 3 ), an iodine-containing precursor, other suitable precursor (which can be used to generate an etchant gas and/or etching plasma), or combinations thereof. In some implementations, a wet etching process implements an etching solution that includes TMAH, NH 4 OH, H 2 O 2 , H 2 SO 4 , HF, HCl, other suitable wet etching constituent, or combinations thereof. Various etching parameters can be tuned to selectively etch isolation layer  140 , active fins  230 A, and/or dummy fins  230 B, such as etchant composition, etching temperature, etching solution concentration, etching time, etching pressure, source power, RF bias voltage, RF bias power, etchant flow rate, other suitable etching parameters, or combinations thereof. The present disclosure contemplates any combination of etching processes and/or other processes for removing portions of active fins  230 A and dummy fins  230 B to define FinFET device regions  250 A- 250 D, as depicted in  FIG. 2F . 
     Turning to  FIG. 2G , an isolation layer  260  is formed over FinFET device  200 . For example, isolation layer  260  covers isolation layer  240  and surfaces of FinFET device  200  that define trench  245  (for example, the end sidewalls of isolation layer  240 , active fins  230 A, dummy fins  230 B, and/or patterning layer  210  and the top surface of substrate  205 ). In furtherance of the example, isolation layer  260  fills a remaining portion of trenches  232 B (such that trenches  232 B are completely filled by isolation layer  240  and isolation layer  260 ) and partially fills trench  245 , though the present disclosure contemplates embodiments where isolation layer  260  partially fills trenches  232 B and/or completely fills trench  245 . Isolation layer  260  is subsequently patterned (which is described in detail below) to form an isolation feature, such as an STI feature, that electrically isolates FinFET device regions  250 A- 250 D from one another. Isolation layer  260  thus includes an isolation material, such as silicon oxide, silicon nitride, silicon oxynitride, other suitable isolation material (for example, including silicon, oxygen, nitrogen, carbon, and/or other suitable isolation constituent), or combinations thereof. In some implementations, the isolation material is a high-k dielectric material (such that isolation layer  260  can be referred to as a high-k dielectric layer), such as hafnium dioxide (HfO 2 ), HfSiO, HfSiON, HfTa 0 , HfTiO, HfZrO, zirconium oxide, aluminum oxide, hafnium dioxide-alumina (HfO 2 —A 1   2 O 3 ) alloy, other suitable high-k dielectric material (for example, including hafnium, lanthanum, aluminum, and/or other suitable high-k dielectric material constituent), or combinations thereof. High-k dielectric material generally refers to dielectric materials having a high dielectric constant, for example, greater than that of silicon oxide (k≈3.9). In the depicted embodiment, isolation layer  260  includes an isolation material that is different than the isolation material of isolation layer  240  to achieve etching selectivity during an etching process, such that isolation layer  260  can be etched without etching (or without significantly etching) isolation layer  240 , and vice versa. For example, isolation layer  260  includes silicon, oxygen, carbon, and nitrogen, such as silicon oxycarbonitride (for example, SiOCN). In another example, isolation layer  260  includes a high-k dielectric material. In some implementations, isolation layer  260  includes a multi-layer structure, such as a bulk dielectric layer disposed over a liner dielectric layer, where the bulk dielectric layer and the liner dielectric layer include materials depending on design requirements. In some implementations, isolation layer  260  includes a dielectric layer disposed over a doped liner layer (including, for example, BSG or PSG). Isolation layer  260  is deposited by CVD, PVD, ALD, HDPCVD, MOCVD, RPCVD, PECVD, LPCVD, ALCVD, APCVD, other suitable deposition process, or combinations thereof. 
     Turning to  FIG. 2H , an isolation layer  265  is formed over FinFET device  200 . Isolation layer  265  fills a remaining portion of trench  245 , such that trench  245  is completely filled by isolation layer  260  and isolation layer  265 . Isolation layer  265  includes an isolation material that is different than the isolation material of isolation layer  260  to achieve etching selectivity during an etching process, such that isolation layer  265  can be etched without etching (or without significantly etching) isolation layer  260 , and vice versa. In the depicted embodiment, isolation layer  265  is formed by a flowable CVD (FCVD) process, which includes depositing a flowable dielectric material (in some implementations, in a liquid state) over isolation layer  260  and converting the flowable dielectric material into a solid dielectric material (for example, by an annealing process). The flowable dielectric material flows into trench  245  and conforms to exposed surfaces of FinFET device  200 , enabling void free filling of trench  245 . For example, the FCVD process introduces a silicon-containing precursor and an oxidizer (collectively referred to as reactants) into a deposition chamber, where the silicon-containing precursor and the oxidizer react and condense onto exposed surfaces of isolation layer  260  to form a flowable dielectric material. In some implementations, the flowable dielectric material is a flowable silicon-oxygen-and-nitrogen containing material, where the flowable silicon-oxygen-and-nitrogen containing material includes Si—OH, Si—H, Si—O, and/or Si—N bonds. An annealing process can convert the flowable silicon-oxygen-and-nitrogen material into a silicon-and-oxygen containing layer, such as a silicon oxide layer. In such embodiments, the annealing process promotes formation of Si—Si and/or Si—O bonds and reduces Si—N and/or Si—H bonds. In some implementations, the annealing process converts Si—OH, Si—H, and/or Si—N bonds into Si—O bonds. In some implementations, the annealing process is a thermal annealing process that heats FinFET device  200  to a temperature that can facilitate conversion of the flowable dielectric material into the solid dielectric material. The thermal annealing process can heat FinFET device  200  via a substrate stage (on which substrate  205  is secured), a lamp source, a laser source, other source, or combinations thereof. In some implementations, the flowable dielectric material is exposed to UV radiation during the annealing process. Alternatively or additionally, isolation layer  265  is formed by a high aspect ratio process (HARP) (implementing, for example, a TEOS precursor and an  3  precursor), HDPCVD (implementing, for example, an SiH 4  precursor and an O 2  precursor), other suitable process, or combinations thereof. Thereafter, a planarization process, such as a chemical mechanical polishing (CMP) process, is performed on the solid dielectric material until reaching and exposing isolation layer  260 . In some implementations, top surfaces of isolation layer  265  and isolation layer  260  are substantially co-planar after the planarization process. In some implementations, an annealing process is subsequently performed to further cure and/or densify isolation layer  265 . 
     Turning to  FIG. 21 , an etch back process is performed on isolation layer  265 . In the depicted embodiment, the etch back process reduces a thickness T 1  of isolation layer  265  to a thickness T 2 , thereby forming a trench  267  between FinFET device regions  250 A,  250 B and FinFET device regions  250 C,  250 D. Trench  267  has sidewalls and a bottom defined by isolation layer  260 . The etch back process is a dry etching process, a wet etching process, or combinations thereof configured to selectively etch isolation layer  265  without (or minimally) etching isolation layer  260 . In some implementations, an etching chemistry of the etch back process is tuned to selectively etch silicon oxide without etching (or without significantly etching) silicon oxycarbonitride or a high-k dielectric material. 
       FIGS. 2J-2L  depict a dummy fin replacement process, where dummy fins  230 B are replaced with dielectric fins. Turning to  FIG. 2J , dummy fins  230 B are removed from FinFET device regions  250 A- 250 D, thereby forming fin openings  270 , which are subsequently filled with a dielectric material as described below. Removing dummy fins  230 B includes depositing a masking layer over isolation layer  260  and isolation layer  265  (in some implementations, the masking layer fills trench  267 ); performing a lithography and etching process, such as those described herein, to define openings in the masking layer that expose dummy fins  230 B (in the depicted embodiment, four opening are formed in the masking layer, where each opening exposes a portion of isolation layer  260  overlying a respective dummy fin  230 B); etching the exposed portion of isolation layer  260 , thereby exposing a portion of isolation layer  240  underlying isolation layer  260  that overlies dummy fins  230 B; etching the exposed portion of isolation layer  240 , thereby exposing patterning layer  210  disposed over dummy fins  230 B; etching the exposed patterning layer  210 , thereby exposing dummy fins  230 ; etching the exposed dummy fins  230 B, thereby forming fin trenches  270 ; and removing the masking layer. In the depicted embodiment, dummy fins  230 B are not completely removed, leaving remainder dummy fins  230 B′ that define bottoms of fin openings  270 . In some implementations, dummy fins  230 B are completely removed, such that the top surface of substrate  205  defines bottoms of fin openings  270 . The masking layer can be removed before or after etching dummy fins  230 B. In some implementations, the masking layer is a resist layer. In some implementations, the masking layer is a hard mask layer, which is formed by depositing a hard mask layer over isolation layer  260  and isolation layer  265  (in some implementations, the hard mask layer fills trench  267 ), forming a patterned resist layer having the opening using a lithography and etching process, such as those described herein, and etching the hard mask layer using the patterned resist layer as an etch mask, such that the patterned hard mask layer includes the opening. In some implementations, the masking layer has a multi-layer structure. 
     Various selective etching processes are performed to etch isolation layer  260 , isolation layer  240 , patterning layer  210 , and dummy fins  230 B to form fin openings  270 . The exposed portion of isolation layer  260  is selectively etched without etching (or without significantly etching) the masking layer and/or isolation layer  240 . For example, an etching chemistry of the etching process is tuned to selectively etch silicon oxycarbonitride or high-k dielectric material without etching (or without significantly etching) silicon oxide and/or resist material. The exposed portion of isolation layer  240  is selectively etched without etching (or without significantly etching) the masking layer, isolation layer  260 , and/or patterning layer  210 . For example, an etching chemistry of the etching process is tuned to selectively etch silicon oxide without etching (or without significantly etching) etching silicon nitride, resist material, silicon oxycarbonitride, and/or high-k dielectric material. The exposed patterning layer  210  disposed over dummy fins  230 B is selectively etched without etching (or without significantly etching) the masking layer, isolation layer  265 , isolation layer  240 , and/or dummy fins  230 B. For example, an etching chemistry of the etching process is tuned to selectively etch silicon nitride and/or silicon oxide without etching (or without significantly etching) etching silicon and/or a resist material. The exposed dummy fins  230 B are selectively etched without etching (or without significantly etching) the masking layer, isolation layer  265 , and/or isolation layer  240 . For example, an etching chemistry of the etching process is tuned to selectively etch silicon without etching (or without significantly etching) silicon oxycarbonitride, high-k dielectric material, silicon oxide, and/or resist material. In the depicted embodiment, since patterning layer  210  includes some constituents in common with isolation layer  265  and isolation layer  240 , isolation layer  265  and/or isolation layer  240  may be partially etched during etching of patterning layer  210 . For example, where pad layer  212  of patterning layer  210  includes silicon oxide, mask layer  214  of patterning layer  210  includes silicon nitride, isolation layer  265  includes silicon oxycarbonitride, and isolation layer  240  includes silicon oxide, etching of patterning layer  210  partially etches isolation layer  265  and/or isolation layer  240  underlying the masking layer, such that fin openings  270  have a first portion having a first width (formed by etching isolation layer  265 , isolation layer  240 , and patterning layer  210 ) disposed over a second portion having a second width (formed by etching dummy fins  230 B), where the first width is greater than the second width. In some implementations, etching mask layer  214  partially etches isolation layer  240  disposed under the masking layer and etching pad layer  212  partially etches isolation layer  240  disposed under the masking layer, which expands a width of fin openings  270 . In some implementations, the selective etching processes utilize a dry etching process that implements a fluorine-containing precursor (for example, CF 4 , SF 6 , NF 3 , CH 2 F 2 , CHF 3 , and/or C 2 F 6 ), an oxygen-containing precursor, a chlorine-containing precursor (for example, Cl 2 , CHCl 3 , CCl 4 , and/or BCl 3 ), a bromine-containing precursor (for example, HBr and/or CHBR 3 ), an iodine-containing precursor, other suitable precursor (which can be used to generate an etchant gas and/or etching plasma), or combinations thereof. In some implementations, the selective etching processes utilize a wet etching process implements an etching solution that includes TMAH, NH 4 OH, H 2 O 2 , H 2 SO 4 , HF, HCl, other suitable wet etching constituent, or combinations thereof. Various etching parameters can be tuned to selectively etch isolation layer  260 , isolation layer  240 , patterning layer  210 , and/or dummy fins  230 B, such as etchant composition, etching temperature, etching solution concentration, etching time, etching pressure, source power, RF bias voltage, RF bias power, etchant flow rate, other suitable etching parameters, or combinations thereof. The present disclosure contemplates any combination of etching processes and/or other processes for removing dummy fins  230 B. 
     Turning to  FIG. 2K , fin openings  270  are filled with a dielectric material. For example, a dielectric layer  280  is formed over FinFET device  200 , and dielectric layer  285  is formed over dielectric layer  280 . In the depicted embodiment, dielectric layer  280  fills fin openings  270  and trench  267 , and dielectric layer  285  is disposed over a top surface of dielectric layer  280 . Dielectric layer  280  and dielectric layer  285  include any suitable dielectric material, such as silicon oxide, silicon nitride, silicon oxynitride, other suitable dielectric material (for example, including silicon, oxygen, nitrogen, carbon, and/or other suitable dielectric constituent), or combinations thereof. In some implementations, the dielectric material is a high-k dielectric material (such that dielectric layer  280  and/or dielectric layer  285  can be referred to as a high-k dielectric layer), such as HfO 2 , HfSiO, HfSiON, HfTaO, HfTiO, HfZrO, zirconium oxide, aluminum oxide, HfO 2 —Al 2 O 3  alloy, other suitable high-k dielectric material (for example, including hafnium, lanthanum, aluminum, and/or other suitable high-k dielectric material constituent), or combinations thereof. A material of dielectric layer  280  is different than a material of dielectric layer  285 . In the depicted embodiment, a material of dielectric layer  280  is the same as a material of isolation layer  260 , and a material of dielectric layer  285  is the same as a material of isolation layer  240 . For example, dielectric layer  280  includes silicon, oxygen, carbon, and/or nitrogen, such as silicon oxycarbonitride or silicon oxycarbide (SiOC), and dielectric layer  285  includes silicon and oxygen, such as silicon oxide. In another example, dielectric layer  280  includes a metal oxide configured as a high-k dielectric material, such as HfO 2 , ZrO 2 or ZrSiO 2 , and dielectric layer  285  includes silicon oxide. The present disclosure further contemplates implementations where a material of dielectric layer  280  is different than a material of isolation layer  260 , and a material of dielectric layer  285  is different than a material of isolation layer  240 . In some implementations, dielectric layer  280  and/or dielectric layer  285  include a multi-layer structure. Dielectric layer  280  and/or dielectric layer  285  is deposited by CVD, PVD, ALD, HDPCVD, MOCVD, RPCVD, PECVD, LPCVD, ALCVD, APCVD, other suitable deposition process, or combinations thereof. 
     Turning to  FIG. 2L , a planarization process, such as a CMP process, is performed until reaching active fins  230 A, such that active fins  230 A function as a planarization (or CMP) stop layer. The planarization process removes any dielectric material overlying (or above) top surfaces of active fins  230 A, such as dielectric layer  285 , a portion of dielectric layer  280 , a portion of isolation layer  260 , a portion of isolation layer  240 , and patterning layer  210  disposed over active fins  230 A, thereby forming dielectric fins  290 , which replace dummy fins  230 B. A width, a length, and a height of dielectric fins  290  is substantially the same as a width, a length, and a height of active fins  230 A. In some implementations, the width is about 6 nm to about 11 nm. In the depicted embodiment, dielectric fins  290  include dielectric layer  280  disposed over remaining dummy fins  230 B′, such that dielectric fins  290  include a dielectric portion disposed over a semiconductor portion. In some implementations, a height of the dielectric portion of dielectric fins  290  (here, dielectric layer  280 ) is about 100 nm to about 200 nm. Alternatively, where dummy fins  230 B are completely removed, dielectric fins  290  include dielectric layer  280 , such that dielectric fins  290  include only the dielectric portion. 
     The planarization process also results in isolation features  240 ′, a dielectric feature  292 A, a dielectric feature  292 B, and an isolation feature  294  of FinFET device  200 . Isolation features  240 ′, which include isolation layer  240 , separate and isolate adjacent fins in each of FinFET device regions  250 A- 250 D. For example, each of FinFET device regions  250 A- 250 D includes two active fins  230 A and one of dielectric fins  290 , which are separated by isolation features  240 ′. Dielectric features  292 A,  292 B, both of which include isolation layer  260 , separate adjacent FinFET device regions along a fin width direction (here, the x-direction). For example, dielectric features  292 A separates FinFET device region  250 A from FinFET device region  250 C, and dielectric feature  292 B separates FinFET device region  250 B from FinFET device region  250 D. Dielectric feature  292 A is disposed between dielectric fins  290  of FinFET device regions  250 A,  250 C, and dielectric feature  292 B is disposed between dielectric fins  290  of FinFET device regions  250 B,  250 D. In some implementations, dielectric features  292 A,  292 B are disposed in isolation features  240 ′, such that isolation features  240 ′ are disposed along sidewalls and bottoms of dielectric features  292 A,  292 B. Isolation feature  294  separates adjacent FinFET device regions along a fin length direction (here, the y-direction). For example, isolation feature  294  separates and isolates FinFET device region  250 A from FinFET device region  250 B and FinFET device region  250 C from FinFET device region  250 D. Isolation feature  294  is disposed between ends of active fins  230 A of FinFET device regions  250 A,  250 B and ends of active fins  230 A of FinFET device regions  250 C,  250 D. In the depicted embodiment, isolation feature  294  includes isolation layer  260 , isolation layer  265 , and isolation layer  280 , where isolation layer  260  is configured as a liner layer of isolation feature  294  and isolation layer  265  and isolation layer  280  are configured as a bulk layer of isolation feature  294 . In some implementations, top surfaces of active fins  230 A, isolation layer  240 , dielectric fins  290 , dielectric feature  292 A, dielectric feature  292 B, and isolation feature  294  are substantially co-planar after the planarization process. 
     Turning to  FIG. 2M , isolation features  240 ′ are recessed, such that active fins  230 A, dielectric fins  290 , dielectric feature  292 A, dielectric feature  292 B, and isolation feature  294  extend (protrude) from between neighboring isolation features  240 ′. For example, isolation features  240 ′ surround a bottom portion of active fins  230 A, thereby defining upper fin active regions of active fins  230 A (generally referring to a portion of active fins  230 A that extend from a top surface of isolation features  240 ′) and lower fin active regions of active fins  230 A (generally referring to a portion of active fins  230 A surrounded by isolation features  240 ′, which extend from a top surface of substrate  205  to the top surface of isolation features  240 ′). In some implementations, an etch back process recesses isolation layer  240  until achieving a desired (target) height of upper fin active regions of active fins  230 A. Isolation features  240 ′ further surround a bottom portion of dielectric fins  290 , dielectric feature  292 A, dielectric feature  292 B, and isolation feature  294 . The etch back process is a dry etching process, a wet etching process, or combinations thereof. The etch back process selectively etches isolation layer  240  without etching (or without significantly etching) active fins  230 A, dielectric fins  290 , dielectric feature  292 A, dielectric feature  292 B, and/or isolation feature  294 . For example, an etching chemistry is tuned to selectively etch silicon oxide without etching (or without significantly etching) silicon, silicon oxycarbonitride, and/or high-k dielectric material. 
     Turning to  FIGS. 2N-2P , fabrication of FinFET device  200  can continue. For example, fabrication can continue with forming a dummy gate, forming epitaxial source/drain features, forming an interlevel dielectric (ILD) layer, replacing the dummy gate with a metal gate, and forming a multilayer interconnect structure. Turning to  FIG. 2N , various gate structures are formed over active fins  230 A and dielectric fins  290 , such as a gate structure  300 A, a gate structure  300 B, a gate structure  300 C, a gate structure  300 D, and a gate structure  300 E. Gate structures  300 A- 300 E extend along the x-direction (for example, substantially perpendicular to active fins  230 A and dielectric fins  290 ) and traverse fin structures of respective FinFET device regions  250 A- 250 D, such that gate structures  300 A- 300 E wrap upper fin active regions of respective active fins  230 A and dielectric fins  290 . Gate structure  300 A is disposed over channel regions of active fins  230 A in FinFET device regions  250 A,  250 C, and gate structure  300 E is disposed over respective channel regions of active fins  230 A in FinFET device regions  250 B,  250 D. Gate structures  300 A,  300 E wrap the channel regions of respective active fins  230 A, thereby interposing respective source/drain regions of respective active fins  230 A. Gate structures  300 A,  300 E engage the channel regions of respective fins  230 A, such that current can flow between the source/drain regions of respective fins  230 A during operation. Gate structure  300 B wraps portions of active fins  230 A in FinFET device regions  250 A,  250 C, positioned such that a source/drain region of active fins  230 A in FinFET device regions  250 A,  250 C is disposed between gate structure  300 B and gate structure  300 A, and gate structure  300 D wraps portions of active fins  230 A in FinFET device regions  250 B,  250 D, positioned such that a source/drain region of active fins  230 A in FinFET device regions  250 B,  250 D is disposed between gate structure  300 D and gate structure  300 E. Gate structures  300 B,  300 D are further partially disposed over isolation feature  294 . Gate structure  300 C is disposed over isolation feature  294 . In some implementations, gate structures  300 A,  300 E are active gate structures, whereas gate structure  300 B- 300 D are dummy gate structures. “Active gate structure” generally refers to an electrically functional gate structure of FinFET device  200 , whereas “dummy gate structure” generally refers to an electrically non-functional gate structure of FinFET device  200 . In some implementations, a dummy gate structure mimics physical properties of an active gate structure, such as physical dimensions of the active gate structure, yet is inoperable (in other words, does not enable current to flow). In some implementations, gate structures  300 B- 300 D enable a substantially uniform processing environment, for example, enabling uniform epitaxial material growth in source/drain regions of active fins  230 A (for example, when forming epitaxial source/drain features), uniform etch rates in source/drain regions of active fins  230 A (for example, when forming source/drain recesses), and/or uniform, substantially planar surfaces (for example, by reducing (or preventing) CMP-induced dishing effects). 
     Gate structures  300 A- 300 E include gate stacks configured to achieve desired functionality according to design requirements of FinFET device  200 , such that gate structures  300 A- 300 E include the same or different layers and/or materials. Gate structures  300 A- 300 E are fabricated according to a gate last process, such that gate structures  300 A- 300 E have dummy gates  302  in  FIG. 2N , which are subsequently replaced with metal gates. Dummy gates  302  include, for example, an interfacial layer  304  (including, for example, silicon oxide), a dummy gate electrode  306  (including, for example, polysilicon), and a hard mask layer  308  (including, for example, silicon nitride). In some implementations, dummy gates  302  include a dummy gate dielectric disposed between dummy gate electrode  306  and interfacial layer  304 . The dummy gate dielectric includes a dielectric material, such as silicon oxide, a high-k dielectric material, other suitable dielectric material, or combinations thereof. Dummy gates  302  can include numerous other layers, for example, capping layers, interface layers, diffusion layers, barrier layers, or combinations thereof. Dummy gates  302  are formed by deposition processes, lithography processes, etching processes, other suitable processes, or combinations thereof. For example, a deposition process is performed to form a dummy gate electrode layer over substrate  205 , particularly over active fins  230 A and dielectric fins  290 . In some implementations, a deposition process is performed to form a dummy gate dielectric layer over active fins  230 A and dielectric fins  290  before forming the dummy gate electrode layer, where the dummy gate electrode layer is formed over the dummy gate dielectric layer. The deposition process includes CVD, PVD, ALD, HDPCVD, MOCVD, RPCVD, PECVD, LPCVD, ALCVD, APCVD, plating, other suitable methods, or combinations thereof. A lithography patterning and etching process is then performed to pattern the dummy gate electrode layer (and, in some implementations, the dummy gate dielectric layer) to form dummy gates  302 , such that dummy gates  302  wrap active fins  230 A as depicted. The lithography patterning processes include resist coating (for example, spin-on coating), soft baking, mask aligning, exposure, post-exposure baking, developing the resist, rinsing, drying (for example, hard baking), other suitable processes, or combinations thereof. Alternatively, the lithography exposing process is assisted, implemented, or replaced by other methods, such as maskless lithography, electron-beam writing, or ion-beam writing. In yet another alternative, the lithography patterning process implements nanoimprint technology. The etching processes include dry etching processes, wet etching processes, other etching methods, or combinations thereof. 
     Turning to  FIG. 20 , processing continues with forming gate spacers  310  of gate structures  300 A- 300 E. Gate spacers  310  are disposed adjacent to (for example, along sidewalls of) dummy gates  302 . In some implementations, gate spacers  310  fill spaces between upper portions of active fins  230 A, dielectric fins  290 , dielectric feature  292 A, and/or dielectric feature  292 B. Gate spacers  310  are formed by any suitable process and include a dielectric material. The dielectric material can include silicon, oxygen, carbon, nitrogen, other suitable material, or combinations thereof (for example, silicon oxide, silicon nitride, silicon oxynitride, or silicon carbide). For example, in the depicted embodiment, a dielectric layer including silicon and nitrogen, such as a silicon nitride layer, can be deposited over substrate  205  and subsequently anisotropically etched to form gate spacers  310 . In some implementations, gate spacers  310  include a multi-layer structure, such as a first dielectric layer that includes silicon nitride and a second dielectric layer that includes silicon oxide. In some implementations, gate spacers  310  include more than one set of spacers, such as seal spacers, offset spacers, sacrificial spacers, dummy spacers, and/or main spacers, formed adjacent to the gate stacks. In such implementations, the various sets of spacers can include materials having different etch rates. For example, a first dielectric layer including silicon and oxygen can be deposited over FinFET device  200  and subsequently anisotropically etched to form a first spacer set adjacent to the gate stacks, and a second dielectric layer including silicon and nitrogen can be deposited over FinFET device  200  and subsequently anisotropically etched to form a second spacer set adjacent to the first spacer set. Implantation, diffusion, and/or annealing processes may be performed to form lightly doped source and drain (LDD) features and/or heavily doped source and drain (HDD) features (both of which are not shown) in source/drain regions of active fins  230 A before and/or after forming gate spacers  310 . 
     Source features and drain features (referred to as source/drain features) are formed in source/drain regions of active fins  230 A. For example, semiconductor material is epitaxially grown on active fins  230 A, forming epitaxial source/drain features  315 . In the depicted embodiment, a fin recess process (for example, an etch back process) is performed on source/drain regions of active fins  230 A, such that epitaxial source/drain features  315  are grown from recessed active fins  230 A′. In some implementations, dielectric fins  290 , dielectric feature  292 A, dielectric feature  292 B, isolation feature  294 , and/or gate spacers  310  disposed between upper portions of active fins  230 A and dielectric fins  290  are partially etched during the fin recess process and/or other etching process, such that a height of dielectric fins  290 , dielectric feature  292 A, dielectric feature  292 B, and/or isolation feature  294  underlying gate structures  300 A- 300 E is greater than a height of dielectric fins  290 , dielectric feature  292 A, dielectric feature  292 B, and/or isolation feature  294  not underlying gate structures  300 A- 300 E. In such implementations, such as depicted in  FIG. 20 , dielectric fins  290  have a first portion having a top surface that is higher than a bottom surface of epitaxial source/drain features  315  and lower than a top surface of epitaxial source/drain features  315  (for example, the portion of dielectric fins  290  underlying gate structures  300 A- 300 E) and a second portion having a top surface that is lower than the bottom surface of epitaxial source/drain features  315  (for example, the portion of dielectric fins  290  not underlying gate structures  300 A- 300 E). In some implementations, source/drain regions of active fins  230  are not subjected to a fin recess process, such that epitaxial source/drain features  315  are grown from and wrap the upper fin active regions of active fins  230 A. In furtherance of the depicted embodiment, epitaxial source/drain features  315  extend (grow) laterally along the x-direction (in some implementations, substantially perpendicular to recessed fins  230 A′), such that epitaxial source/drain features  315  are merged epitaxial source/drain features that span more than one recessed active fin  230 A′. In some implementations, epitaxial source/drain features  315  include partially merged portions (with interruption (or gaps) between epitaxial material grown from adjacent recessed active fins  230 A′) and/or fully merged portions (without interruption (or gaps) between epitaxial material grown from adjacent recessed active fins  230 ′). 
     An epitaxy process can implement CVD deposition techniques (for example, vapor-phase epitaxy (VPE), ultra-high vacuum CVD (UHV-CVD), LPCVD, and/or PECVD), molecular beam epitaxy, other suitable SEG processes, or combinations thereof. The epitaxy process can use gaseous and/or liquid precursors, which interact with the composition of recessed active fins  230 A′. Epitaxial source/drain features  315  are doped with n-type dopants and/or p-type dopants. In the depicted embodiment, epitaxial source/drain features  315  are configured depending on a type of FinFET fabricated in their respective FinFET device region. For example, in FinFET device regions  250 A- 250 D that are configured for n-type FinFETs, epitaxial source/drain features  315  can include epitaxial layers including silicon and/or carbon, where silicon-containing epitaxial layers or silicon-carbon-containing epitaxial layers are doped with phosphorous, arsenic, other n-type dopant, or combinations thereof (for example, forming an Si:P epitaxial layer, an Si:C epitaxial layer, or an Si:C:P epitaxial layer). In furtherance of the example, in FinFET device regions  250 A- 250 D that are configured for p-type FinFETs, epitaxial source/drain features  315  can include epitaxial layers including silicon and/or germanium, where the silicon germanium containing epitaxial layers are doped with boron, carbon, other p-type dopant, or combinations thereof (for example, forming an Si:Ge:B epitaxial layer or an Si:Ge:C epitaxial layer). In some implementations, epitaxial source/drain features  315  include materials and/or dopants that achieve desired tensile stress and/or compressive stress in the channel regions. In some implementations, epitaxial source/drain features  315  are doped during deposition by adding impurities to a source material of the epitaxy process. In some implementations, epitaxial source/drain features  315  are doped by an ion implantation process subsequent to a deposition process. In some implementations, annealing processes are performed to activate dopants in epitaxial source/drain features  315  and/or other source/drain features of FinFET device  200 , such as HDD regions and/or LDD regions. 
     Turning to  FIG. 2P , an ILD layer  320  is formed over FinFET device  200 , particularly over epitaxial source/drain features  315 , gate structures  300 A- 300 E, dielectric fins  290 , dielectric feature  292 A, dielectric feature  292 B, and isolation feature  294 . In some implementations, ILD layer  320  is a portion of a multilayer interconnect (MLI) feature that electrically couples various devices (for example, transistors, resistors, capacitors, and/or inductors) and/or components (for example, gate structures and/or source/drain features) of FinFET device  200 , such that the various devices and/or components can operate as specified by design requirements of FinFET device  200 . ILD layer  320  includes a dielectric material including, for example, silicon oxide, silicon nitride, silicon oxynitride, TEOS formed oxide, PSG, BPSG, low-k dielectric material, other suitable dielectric material, or combinations thereof. Exemplary low-k dielectric materials include FSG, carbon doped silicon oxide, Black Diamond® (Applied Materials of Santa Clara, California), Xerogel, Aerogel, amorphous fluorinated carbon, Parylene, BCB, SILK (Dow Chemical, Midland, Michigan), polyimide, other low-k dielectric material, or combinations thereof. In some implementations, ILD layer  320  has a multilayer structure having multiple dielectric materials. In some implementations, a contact etch stop layer (CESL) is disposed between ILD layer  320  and epitaxial source/drain features  315 , gate structures  300 A- 300 E, dielectric fins  290 , dielectric feature  292 A, dielectric feature  292 B, and/or isolation feature  294 . The CESL includes a material different than ILD layer  320 , such as a dielectric material that is different than the dielectric material of ILD layer  320 . In the depicted embodiment, where ILD layer  320  includes a low-k dielectric material, the CESL includes silicon and nitrogen (for example, silicon nitride or silicon oxynitride). ILD layer  320  and/or the CESL is formed, for example, by a deposition process (such as CVD, PVD, ALD, FCVD, HDPCVD, MOCVD, RPCVD, PECVD, LPCVD, ALCVD, APCVD, plating, other suitable methods, or combinations thereof). Subsequent to the deposition of ILD layer  320  and/or the CESL, a CMP process and/or other planarization process is performed, such that a top portion of dummy gates  310  of gate structure  300 A- 300 E (here, hard mask layers  308 ) is reached (exposed). 
     Dummy gates  302  of gate structures  300 A- 300 E are then replaced with metal gates  330 . In some implementations, dummy gates  302  are removed to form gate openings in gate structures  300 A- 300 E (for example, having sidewalls defined by gate spacers  310 ) that expose upper fin active regions of a portion of active fins  230 A and an upper portion of dielectric fins  290 . In some implementations, a portion of dummy gates  302  is removed, such that gate openings expose an interfacial layer and/or a gate dielectric (and, in some implementations, a dummy gate dielectric) of dummy gates  302 . The etching process is a dry etching process, a wet etching process, or combinations thereof. In some implementations, an etching process selectively removes dummy gates  302  without etching (or without significantly) etching ILD layer  320 , gate spacers  310 , and/or other features of FinFET device  200 . In some implementations, a selective etching process can be tuned, such that dummy gate electrodes  306  (including, for example, polysilicon) are etched without etching (or without significantly etching) an interfacial layer and/or a dummy gate dielectric of dummy gates  302 , gate spacers  310 , ILD layer  320 , and/or other feature of FinFET device  200 . Metal gates  310  are then formed in the gate openings. Metal gates  310  are configured to achieve desired functionality according to design requirements of FinFET device  200 , such that gate structures  300 A- 300 E include the same or different layers and/or materials. In the depicted embodiment, metal gates  310  include gate dielectrics  332  and gate electrodes  334 . In implementations where gate structures  300 A- 300 E span a p-type FinFET and an n-type FinFET (for example, where FinFET device regions  250 A,  250 B are configured with p-type FinFETs and FinFET device regions  250 C,  250 D are configured with n-type FinFETs, or vice versa), the present disclosure contemplates that gate structures  300 A- 300 E can include different layers in regions corresponding with the p-type FinFET and the n-type FinFET. For example, a number, configuration, and/or materials of layers of gate dielectrics  332  and/or gate electrodes  334  in FinFET device regions  250 A,  250 B may be different than a number, configuration, and/or materials of layers of gate dielectrics  332  and/or gate electrodes  334  in FinFET device regions  250 C,  250 D. In some implementations, isolation features  338  are formed to separate metal gates  330  of FinFET device regions  250 A,  250 C and metal gates  330  of FinFET device regions  250 B,  250 D. Isolation features  338  are formed by any suitable process, and in some implementations, include a dielectric material. 
     Gate dielectrics  332  include a dielectric material, such as silicon oxide, high-k dielectric material, other suitable dielectric material, or combinations thereof. Gate dielectrics  332  wrap upper fin active regions of a portion of active fins  230 A and an upper region of a portion of dielectric fins  290 . In the depicted embodiment, gate dielectrics  332  includes one or more high-k dielectric layers including, for example, hafnium, aluminum, zirconium, lanthanum, tantalum, titanium, yttrium, oxygen, nitrogen, other suitable constituent, or combinations thereof. In some implementations, the one or more high-k dielectric layers include HfO 2 , HfSiO, HfSiON, HffaO, HMO, HfZrO, ZrO 2 Al 2 O 3 , HfO 2 —Al 2 O 3 , TiO 2 , Ta 2 O 5 , L 2 O 3 , Y 2 O 3 , other suitable high-k dielectric material, or combinations thereof. In some implementations, gate dielectrics  332  further include an interfacial layer (including a dielectric material, such as silicon oxide) disposed between the high-k dielectric layer and respective active fins  230 A and isolation features  240 ′. In some implementations, gate dielectrics  332  are configured to tune work functions of respective FinFETs in FinFET device regions  250 A- 250 D according to design requirements of FinFET device  200 . Gate dielectrics  332  are formed by various processes, such as ALD, CVD, PVD, and/or other suitable process. 
     Gate electrodes  334  are respectively disposed over gate dielectrics  332 . Gate electrodes  334  include an electrically conductive material. In some implementations, gate electrodes  334  includes multiple layers, such as one or more capping layers, work function layers, glue/barrier layers, and/or metal fill (or bulk) layers. A capping layer can include a material that prevents or eliminates diffusion and/or reaction of constituents between gate dielectrics  332  and other layers of gate structures  300 A- 300 E (in particular, gate layers including metal). In some implementation, the capping layer includes a metal and nitrogen, such as titanium nitride (TiN), tantalum nitride (TaN), tungsten nitride (W 2 N), titanium silicon nitride (TiSiN), tantalum silicon nitride (TaSiN), or combinations thereof. A work function layer can include a conductive material tuned to have a desired work function (such as an n-type work function or a p-type work function), such as n-type work function materials and/or p-type work function materials. P-type work function materials include TiN, TaN, Ru, Mo, Al, WN, ZrSi2, MoSi 2 , TaSi 2 , NiSi 2 , WN, other p-type work function material, or combinations thereof. N-type work function materials include Ti, Al, Ag, Mn, Zr, TiAl, TiA 1 C, TaC, TaCN, TaSiN, TaAl, TaA 1 C, TiAlN, other n-type work function material, or combinations thereof. A glue/barrier layer can include a material that promotes adhesion between adjacent layers, such as the work function layer and the metal fill layer, and/or a material that blocks and/or reduces diffusion between gate layers, such as such as the work function layer and the metal fill layer. For example, the glue/barrier layer includes metal (for example, W, Al, Ta, Ti, Ni, Cu, Co, other suitable metal, or combinations thereof), metal oxides, metal nitrides (for example, TiN), or combinations thereof. A metal fill layer can include a suitable conductive material, such as Al, W, and/or Cu. In some implementations, a hard mask layer (including, for example, silicon nitride or silicon carbide) is disposed over gate electrodes  334 . Gate electrodes  334  are formed by various deposition processes, such as ALD, CVD, PVD, and/or other suitable process. 
     Various contacts can be formed to facilitate operation of FinFET device  200 . For example, fabrication of the MLI feature can continue. The MLI feature includes a combination of dielectric layers (including ILD layer  320 ) and electrically conductive layers (for example, metal layers) configured to form various interconnect structures. The conductive layers are configured to form vertical interconnect features, such as device-level contacts and/or vias, and/or horizontal interconnect features, such as conductive lines. Vertical interconnect features typically connect horizontal interconnect features in different layers (or different planes) of the MLI feature. During operation of FinFET device  200 , the interconnect features are configured to route signals between the devices and/or the components of FinFET device  200  and/or distribute signals (for example, clock signals, voltage signals, and/or ground signals) to the devices and/or the components of FinFET device  200 . The present disclosure contemplates the MLI feature including any number and/or configuration of dielectric layers and/or conductive layers depending on design requirements of FinFET device  200 . 
     In the depicted embodiment, device-level contacts  340 , vias (not shown), and conductive lines (not shown) are formed in ILD layer  320  and/or other ILD layers of the MLI feature to form interconnect structures. Device-level contacts  340  (also referred to as local interconnects or local contacts) electrically couple and/or physically couple IC device features, such as features of FinFETs in FinFET device regions  250 A- 250 D. For example, device-level contacts  340  are metal-to-device (MD) contacts, which generally refer to contacts to a conductive region, such as source/drain regions, of FinFET device  200 . In the depicted embodiment, device-level contacts  340  are disposed on respective epitaxial source/drain features  315 , such that device-level contacts  340  physically (or directly) connect the source/drain regions of FinFETs in FinFET device regions  250 A- 250 D to the MLI feature (for example, to respective vias). Device-level contacts  340 , vias, and conductive lines include any suitable electrically conductive material, such as Ta, Ti, Al, Cu, Co, W, TiN, TaN, other suitable conductive materials, or combinations thereof. Various conductive materials can be combined to provide device-level contacts  340 , vias, and/or conductive lines with various layers, such as one or more barrier layers, adhesion layers, liner layers, bulk layers, other suitable layers, or combinations thereof. In some implementations, device-level-contacts  340  include Ti, TiN, and/or Co; vias include Ti, TiN, and/or W; and conductive lines include Cu, Co, and/or Ru. Device-level contacts  340 , vias, and conductive lines are formed by patterning ILD layer  320  and/or other ILD layers of the MLI feature. Patterning the ILD layers can include lithography processes and/or etching processes to form openings (trenches), such as contact openings, via openings, and/or line openings in respective ILD layers. In some implementations, the lithography processes include forming a resist layer over respective ILD layers, exposing the resist layer to patterned radiation, and developing the exposed resist layer, thereby forming a patterned resist layer that can be used as a masking element for etching opening(s) in respective ILD layers. The etching processes include dry etching processes, wet etching processes, other etching processes, or combinations thereof. Thereafter, the opening(s) are filled with one or more conductive materials. The conductive material(s) can be deposited by PVD, CVD, ALD, electroplating, electroless plating, other suitable deposition process, or combinations thereof. Thereafter, any excess conductive material(s) can be removed by a planarization process, such as a CMP process, thereby planarizing a top surface of the ILD layers (for example, ILD layer  320 ), device-level contacts  340 , vias, and/or conductive lines. The present disclosure contemplates any configuration of device-level contacts, vias, and/or conductive lines. 
     Fin-like field effect transistor (FinFET) patterning methods are disclosed herein for achieving fin width uniformity. Though method  100  is applied herein to form fins of FinFET devices of FinFET device  200 , method  100  can be applied in numerous ways to form other IC features of IC devices. As one of many examples, the patterning techniques disclosed herein can be implemented to form gate features and/or other IC features with reduced etching loading effects. The present disclosure provides for many different embodiments. 
     An exemplary method includes forming a mandrel layer over a substrate and performing a first cut to remove a portion of the mandrel layer, thereby leaving a mandrel feature and a dummy mandrel feature disposed over the substrate. The dummy mandrel feature is disposed directly adjacent to the mandrel feature. The substrate is etched using the mandrel feature and the dummy mandrel feature as an etch mask, thereby forming a dummy fin feature and an active fin feature. The dummy fin feature is separated from the active fin feature by a first spacing along a first direction. A second cut is then performed to remove a portion of the dummy fin feature and a portion of the active fin feature, thereby forming dummy fins separated by a second spacing and active fins separated by the second spacing. The second spacing is along a second direction that is substantially perpendicular to the first direction. A third cut is then performed to remove the dummy fins, thereby forming fin openings. The fin openings are filled with a dielectric material, such as a high-k dielectric material or a material that includes silicon, oxygen, and carbon, thereby forming dielectric fins. In some implementations, the method further includes forming a first isolation layer over the dummy fin feature and the active fin feature before performing the second cut and forming a second isolation layer over the first isolation layer after performing the second cut. The first isolation layer fills a trench defined between the dummy fin feature and the active fin feature. A material of the second isolation layer is different than a material of the first isolation layer. 
     In some implementations, the mandrel feature is a first mandrel feature, the dummy mandrel feature is a first dummy mandrel feature, the dummy fin feature is a first dummy fin feature, the active fin feature is a first active fin feature, the dummy fins are first dummy fins, the active fins are first active fins, the fin openings are first fin openings, and the dielectric fins are first dielectric fins. In such implementations, performing the first cut can further include leaving a second mandrel feature and a second dummy mandrel feature disposed over the substrate. The second dummy mandrel feature is disposed directly adjacent to the second mandrel feature. In such implementations, etching the substrate can further include using the second mandrel feature and the second dummy mandrel feature as an etch mask, thereby forming a second dummy fin feature and a second active fin feature separated by the first spacing. In such implementations, performing the second cut can further include removing a portion of the second dummy fin feature and a portion of the second active fin feature, thereby forming second dummy fins separated by the second spacing and second active fins separated by the second spacing. In such implementations, performing the third cut can further include removing the second dummy fins, thereby forming second fin openings. In such implementations, filling the fin openings can further include forming second dielectric fins, wherein the first dielectric fins are separated from the second dielectric fins by a third spacing along the first direction, wherein the third spacing is greater than the first spacing. 
     In some implementations, the trench defined between the dummy fin feature and the active fin feature is a first trench defined between the first dummy fin feature and the first active fin feature. In such implementations, forming the first isolation layer can further include forming the first isolation layer over the second dummy fin feature and the second active fin feature, wherein the first isolation layer fills a second trench defined between the second dummy fin feature and the second active fin feature and partially fills a third trench defined between the second dummy fin feature and the first dummy fin feature. In such implementations, forming the second isolation layer over the first isolation layer can further include filling a remaining portion of the third trench and partially filling a fourth trench defined between ends of the first active fins, ends of the first dummy fins, ends of the second active fins, and ends of the second dummy fins. In some implementations, the method further includes forming a third isolation layer over the second isolation layer, wherein the third isolation layer partially fills the fourth trench and a material of the third isolation layer is different than a material of the first isolation layer and the second isolation layer. 
     In some implementations, performing the third cut includes performing a selective etch process to remove a portion of the second isolation layer and the first isolation layer to expose the first dummy fins and the second dummy fins and performing a selective etch process to remove the exposed first dummy fins and the exposed second dummy fins. In some implementations, filling the fin openings includes depositing a dielectric layer over the first isolation layer, the second isolation layer, and the third isolation layer and performing a planarization process to remove a portion of the dielectric layer, a portion of the second isolation layer, and a portion of the first isolation layer, thereby exposing the first active fins and the second active fins. The dielectric layer fills the first fin openings, the second fin openings, and a remaining portion of the fourth trench, and further wherein a material of the dielectric layer is the same as a material of the second isolation layer. 
     Another exemplary method includes forming a mandrel layer over a substrate and performing a fin cut process to pattern the mandrel layer to define a first fin active region and a second fin active region. The mandrel layer includes an array of mandrels separated by a first spacing, and the fin cut process removes a portion of the mandrel layer, such that a first mandrel and a first dummy mandrel of the array of mandrels remain over the substrate defining the first fin active region and a second mandrel and a second dummy mandrel of the array of mandrels remain over the substrate defining the second fin active region. The first dummy mandrel and the second dummy mandrel are separated by a second spacing that is greater than the first spacing. The first dummy mandrel and the second dummy mandrel are disposed between the first mandrel and the second mandrel. The method further includes etching the substrate using the patterned mandrel layer as an etch mask to form a first active fin feature and a first dummy fin feature in the first fin active region and a second active fin feature and a second dummy fin feature in the second fin active region. The method further includes performing a fin end cut process to pattern the first active fin feature, the first dummy fin feature, the second active fin feature, and the second dummy fin feature, thereby dividing the first active fin feature into first fins separated by an end-to-end spacing, the first dummy fin feature into first dummy fins separated by the end-to-end spacing, the second active fin feature into second fins separated by the end-to-end spacing, and the second dummy fin feature into second dummy fins separated by the end-to-end spacing. The method further includes replacing the first dummy fins and the second dummy fins with dielectric fins. 
     In some implementations, the method further includes forming a first isolation layer over the first active fin feature, the second active fin feature, the first dummy fin feature, and the second dummy fin feature before performing the fin end cut process. The first isolation layer fills first trenches defined between the first fin feature and the first dummy fin feature and between the second active fin feature and the second dummy fin feature. The first isolation layer also partially fills a second trench defined between the first dummy fin feature and the second dummy fin feature. In some implementations, the first isolation layer is etched back to form isolation features that isolate the first fins and the second fins from the dielectric fins. In some implementations, the method further includes forming a second isolation layer over the first isolation layer after performing the fin end cut process. The second isolation layer fills a remaining portion of the second trench and partially fills a third trench defined between ends of the first fins, ends of the first dummy fins, ends of the second fins, and ends of the second fins. In some implementations, the method further includes forming a third isolation layer over the second isolation layer. The third isolation layer partially fills the third trench. In some implementations, the third isolation layer is formed by performing a flowable chemical vapor deposition (FCVD) process to deposit an isolation material that fills the third trench and etching back the isolation material. In some implementations, the first dummy fins and the second dummy fins are replaced with dielectric fins by etching a portion of the second isolation layer and the first isolation layer, Exposed first dummy fins and the second dummy fins are then etched to form fin openings, which are filled with a dielectric material. In some implementations, filling the fin openings with the dielectric layer includes depositing a dielectric layer over the first isolation layer, the second isolation layer, and the third isolation layer and performing a planarization process until reaching the first fins and the second fins. The dielectric layer fills the fin openings and a remaining portion of the third trench. 
     An exemplary integrated circuit device includes a fin-like field effect transistor (FinFET) device having a fin structure that includes a dielectric fin and an active fin extending along a first direction. The dielectric fin is disposed directly adjacent to the active fin. A width of the dielectric fin is substantially the same as a width of the active fin. An isolation feature is disposed between the dielectric fin and the active fin. A dielectric material of the dielectric fin is different than a dielectric material of the isolation feature. A gate structure is disposed over a portion of the dielectric fin and the active fin, wherein the gate structure extends along a second direction that is substantially perpendicular to the first direction. 
     In some implementations, the FinFET device is a first FinFET device, the fin structure is a first fin structure, the dielectric fin is a first dielectric fin, the active fin is a first active fin, and the isolation feature is a first isolation feature. In such implementations, the integrated circuit device further includes a second FinFET device having a second fin structure that includes a second dielectric fin and a second active fin extending along the first direction. The second dielectric fin is disposed directly adjacent to the second active fin. A width of the second dielectric fin is substantially the same as a width of the second active fin. A second isolation feature is disposed between the second dielectric fin and the second active fin. A dielectric material of the second dielectric fin is different than a dielectric material of the second isolation feature. In furtherance of such implementations, the gate structure is further disposed over a portion of the second dielectric fin and the second active fin, the first active fin and the first dielectric fin are separated by a first spacing, the second active fin and the second dielectric fin are separated by the first spacing, and the first dielectric fin and the second dielectric fin are disposed between the first active fin and the second active fin. The first dielectric fin and the second dielectric fin are separated by a second spacing that is greater than the first spacing. In some implementations, the integrated circuit device further includes a dielectric feature disposed between the first dielectric fin and the second dielectric fin. A width of the dielectric feature is greater than the width of the first dielectric fin and the width of the second dielectric fin. In some implementations, the dielectric feature is separated from the first dielectric fin and the second dielectric fin by the first spacing. 
     The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure.