Patent Publication Number: US-2022238429-A1

Title: Semiconductor devices and methods of manufacturing thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of U.S. Provisional Application No. 63/142,033, filed Jan. 27, 2021, entitled “SYSTEMS AND METHODS FOR PROVIDING A CROSS-LAYER MEOL DCAP HAVING LIMITED LEAKAGE,” which is incorporated herein by reference in its entirety for all purposes. 
    
    
     BACKGROUND 
     During the operation of certain integrated circuits, power supply lines may supply transient currents with a relatively high intensity. These conditions can result in noise on the power supply lines. For example, the voltage on the power supply line may fluctuate when the transition time of the transient current is particularly short or when the line&#39;s parasitic inductance or parasitic resistance is large. To ameliorate such conditions, decoupling capacitors are typically used, acting as temporary charge reservoirs to prevent momentary fluctuations in supply voltage. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion. 
         FIG. 1  illustrates an example layout design of a semiconductor device that includes a number of interlayer decoupling capacitors, in accordance with some embodiments. 
         FIGS. 2A and 2B  respectively illustrate a perspective and cross-sectional view of a semiconductor device made based on the layout design of  FIG. 1 , in accordance with some embodiments. 
         FIG. 3  illustrates a flowchart of a method of manufacturing a semiconductor device, in accordance with some embodiments. 
         FIG. 4  illustrates a block diagram of a system of generating an IC layout design, in accordance with some embodiments. 
         FIG. 5  illustrates a block diagram of an IC manufacturing system, and an IC manufacturing flow associated therewith, in accordance with some embodiments. 
         FIG. 6  illustrates a flow chart of an example method for making a semiconductor device that includes a number of interlayer decoupling capacitors, in accordance with some embodiments. 
         FIGS. 7, 8, 9, 10, 11, and 12  illustrate cross-sectional views of an example semiconductor device (or a portion of the example semiconductor device) during various fabrication stages, made by the method of  FIG. 6 , in accordance with some embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. 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. 
     Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated  90  degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly. 
     The semiconductor industry has experienced rapid growth in the past several decades. Technological advances in semiconductor materials and design have produced increasingly smaller and more complex circuits. These material and design advances have been made possible as the technologies related to processing and manufacturing have also undergone technical advances. In the course of semiconductor evolution, the number of interconnected devices per unit of area has increased as the size of the smallest component that can be reliably created has decreased. 
     Many of the technological advances in semiconductors have occurred in the field of integrated circuits, and some of these involve capacitors. During the operation of certain circuits, power supply lines (sometimes referred to as power rails) may supply transient currents with a relatively high intensity. These conditions can result in noise on the power supply lines. The voltage on the power supply line may fluctuate when the transition time of the transient current is particularly short or when the line&#39;s parasitic inductance or parasitic resistance is large. To ameliorate such conditions, decoupling capacitors may be used, acting as temporary charge reservoirs to prevent momentary fluctuations in supply voltage. 
     In general, an integrated circuit has a number of circuits, some of which may be formed by a first type of devices (e.g., transistors) that operate under a relatively low voltage (e.g., not higher than 0.9 volts (V)), and some of which may be formed by a second type of devices (e.g., transistors) that operate under a relatively high voltage (e.g., around 1.2V). The first type of transistors may sometimes be referred to as core transistors; and the second type of transistor may sometime be referred to as input/output (I/O) transistors. The circuits formed by the core transistors may include, for example, logic circuits, static random access memory (SRAM) circuits, and/or ring oscillators (ROs); and the circuits formed by the I/O transistors may include, for example, input/output (I/O) circuits, and/or serializer/deserializer (SerDes). 
     The core transistors are typically formed in a relatively denser area of a substrate (sometimes referred to as a core area), while the I/O transistors are typically formed in a relatively sparser area of the substrate (sometimes referred to as an I/O area). Over the core area, a number of interconnect structures, operatively coupled to the core transistors, can be formed in a relatively higher density; and over the I/O area, a number of interconnect structures, operatively coupled to the I/O transistors, can be formed in a relatively lower density. In the existing technologies, the decoupling capacitors are commonly formed by the interconnect structures within a same layer (sometimes referred to as intralayer decoupling capacitors) in the I/O area to minimize leakage current, even with a trade-off of a lower density. While evolving into the next generation of technology nodes (of transistors), concepts of replacing I/O transistors with core transistors (i.e., including only core transistors over a substrate) have been proposed to further increase an integration density of the transistors. As such, the decoupling capacitors formed by the interconnect structures within the same layer in such universal core areas disadvantageously encounter various issues such as, for example, undesirable high leakage current. Thus, decoupling capacitors on certain integrated circuits have not been entirely satisfactory to date and may pose increasing problems in the near future. 
     The present disclosure provides various embodiments of a number of decoupling capacitors, each of which is formed across various layers of a semiconductor device. In various embodiments, such a decoupling capacitor may sometimes be referred to as a cross-layer decoupling capacitor, a vertically integratable decoupling capacitor, or an interlayer decoupling capacitor. For example, a first decoupling capacitor may include a first electrode that is an interconnect structure disposed in the bottommost one of a number of back-end-of-line (BEOL) layers and a second electrode that is one of a number of interconnect structures within a middle-end-of-line (MEOL) layer, typically one layer below the bottommost BEOL layer. A second decoupling capacitor may include a first electrode that is the interconnect structure M 0  and a second electrode that is a conductive structure (e.g., a metal gate structure) within a front-end-of-line (FEOL) layer, typically one layer below the MEOL layer. A third decoupling capacitor may include a first electrode that is the interconnect structure M 0  and a second electrode that is a conductive structure/region (e.g., epitaxial source/drain structures) within the FEOL layer. 
     By vertically integrating conductive structures across different layers to form the interlayer decoupling capacitors, as disclosed herein, a density of the total decoupling capacitors can significantly increase within a certain area of a substrate. For example, in an integrated circuit that only has core transistors, dimensions (e.g., widths) of the interconnect structures in the BEOL layers typically shrink with dimensions of the core transistors accordingly to account for the lower operation voltage of the transistors in the FEOL layer. By incorporating the interlayer decoupling capacitors into the total decoupling capacitors, a density of the decoupling capacitors can be increased by at least 1.3 times than the scenario that only includes intralayer decoupling capacitors. Even in some scenarios where the dimensions of the BEOL interconnect structures do not shrink accordingly, with the interlayer decoupling capacitors, a density of the decoupling capacitors can be increased by at least 1.7 times than the scenario that only includes intralayer decoupling capacitors. Further, by tying one of the electrodes of each the disclosed decoupling capacitors to a power supply, leakage current, if any, induced by the decoupling capacitor can significantly decrease. Thus, the trade-off between the density and leakage current of decoupling capacitors that the existing technologies commonly face can be avoided. 
     Referring first to  FIG. 1 , an example layout design  100  of a portion of a semiconductor device (e.g., an integrated circuit) is depicted, in accordance with various embodiments. The layout design  100  may be used to fabricate at least a portion of a semiconductor device that includes one or more of the disclosed interlayer decoupling capacitors. It should be understood that the layout design  100  is simplified for purposes of illustration and thus, the layout design  100  of  FIG. 1  is not limited to any circuit and can include any of various other patterns/features, while remaining within the scope of the present disclosure. 
     The semiconductor device that can be fabricated out of the layout design  100  may include an active region. Such an active region may be a fin-shaped structure of one or more fin field-effect-transistors (FinFETs), a number of nanostructures (e.g., nanosheets, nanowires, etc.) of one or more gate-all-around (GAA) transistors, or an oxide-definition/diffusion (OD) region of one or more planar metal-oxide-semiconductor field-effect-transistors (MOSFETs), in which the active region may serve as a channel, a source feature, or a drain feature of the respective transistor(s). In some embodiments, the transistors formed in the active region may operate under a relatively low voltage, e.g., not higher than 0.9 volts (V). Such transistors are sometimes referred to as “core transistors.” 
     As shown in  FIG. 1 , the layout design  100  includes a pattern  102 . The pattern  102  may extend along a first lateral direction (e.g., the X axis in  FIG. 1 ). In some embodiments, the pattern  102  is configured to form an active region over a substrate, hereinafter “active region pattern  102 .” The active region pattern  102  may be characterized with a conduction type, for example, a p-type doped region or an n-type doped region. The layout design  100  can be used to form a number of transistors in various configurations. In one example where the transistors are to be formed as FinFETs, the active region pattern  102  may be used to form a p-type or n-type fin-based structure over a substrate. In another example where the transistor are to be formed as GAA transistors, the active region pattern  102  may be used to form one or more p-type or n-type nanostructures stacked on top of one another over a substrate. In yet another example where the transistors are to be formed as planar MOSFETs, the active region pattern  102  may be used to form a p-type or n-type region recessed in a substrate (e.g., a well). 
     The layout design  100  further includes patterns  104 ,  106 ,  108 ,  110 ,  112 , and  114 . The patterns  104  to  114  may extend along a second lateral direction (e.g., the Y axis of  FIG. 1 ). Although the patterns  104 - 114  are each shown as a continuous pattern extending along the Y axis in  FIG. 1 , it should be understood that the patterns  104 - 114  can each be “cut” into a number of segments (based on functionality of the completed semiconductor device), while remaining within the scope of the present disclosure. The patterns  104  to  114  are each configured to form a gate structure, hereinafter “gate structure pattern  104 ,” “gate structure pattern  106 ,” “gate structure pattern  108 ,” “gate structure pattern  110 ,” “gate structure pattern  112 ,” and “gate structure pattern  114 ,” respectively. Each of the gate structure patterns  104  to  114  can overlay a respective portion of the active region pattern  102  to define one device (e.g., transistor). 
     In accordance with various embodiments, the gate structure patterns (e.g.,  104 ,  106 ,  112 ,  114 ) disposed closer to either side of the active region pattern  102  may be configured to form transistors that can at least in part form one or more of the interlayer decoupling capacitors of the semiconductor device, and the gate structure patterns (e.g.,  108 ,  110 ) disposed farther from either side of the active region pattern  102  may be configured to form transistors that can at least in part form one or more active circuits of the semiconductor device. Hereinafter, the area that houses the gate structure patterns  104 ,  106 ,  112  and  114  may sometimes be referred to as “decoupling capacitor (DCAP) area,” and the area that houses the gate structure patterns  108  and  110  may sometimes be referred to as “active circuit area.” 
     For example, the portion of the gate structure pattern  104  that overlays the active region pattern  102  can define the gate feature of a transistor  105 , and the portions of the active region pattern  102  that are disposed on the left-hand side ( 120 ) and right-hand side ( 122 ) of the gate structure pattern  104  can define the source and drain features of the transistor  105 , respectively. The portion of the gate structure pattern  106  that overlays the active region pattern  102  can define the gate feature of a transistor  107 , and the portions of the active region pattern  102  that are disposed on the left-hand side ( 122 ) and right-hand side ( 124 ) of the gate structure pattern  106  can define the source and drain features of the transistor  107 , respectively. The portion of the gate structure pattern  108  that overlays the active region pattern  102  can define the gate feature of a transistor  109 , and the portions of the active region pattern  102  that are disposed on the left-hand side ( 124 ) and right-hand side ( 126 ) of the gate structure pattern  108  can define the source and drain features of the transistor  109 , respectively. The portion of the gate structure pattern  110  that overlays the active region pattern  102  can define the gate feature of a transistor  111 , and the portions of the active region pattern  102  that are disposed on the left-hand side ( 128 ) and right-hand side ( 130 ) of the gate structure pattern  110  can define the source and drain features of the transistor  111 , respectively. The portion of the gate structure pattern  112  that overlays the active region pattern  102  can define the gate feature of a transistor  113 , and the portions of the active region pattern  102  that are disposed on the left-hand side ( 130 ) and right-hand side ( 132 ) of the gate structure pattern  112  can define the source and drain features of the transistor  113 , respectively. The portion of the gate structure pattern  114  that overlays the active region pattern  102  can define the gate feature of a transistor  115 , and the portions of the active region pattern  102  that are disposed on the left-hand side ( 132 ) and right-hand side ( 134 ) of the gate structure pattern  114  can define the source and drain features of the transistor  115 , respectively. 
     The layout design  100  further includes patterns  144 ,  146 , and  148 . The patterns  144 ,  146 , and  148  may extend along the second lateral direction (e.g., the Y axis in  FIG. 1 ), i.e., in parallel with the gate structure patterns  104 - 114 . Further, the patterns  144 - 148  may be sandwiched between adjacent ones of the gate structure patterns  104 - 114 . Although the patterns  144 - 148  are each shown as a continuous pattern extending along the Y axis in  FIG. 1 , it should be understood that the patterns  144 - 148  can each be “cut” into a number of segments (based on functionality of the completed semiconductor device), while remaining within the scope of the present disclosure. The patterns  144 ,  148 , and  150  are each configured to form a source/drain interconnect structure (e.g., “MD”), hereinafter “MD pattern  144 ,” “MD pattern  146 ,” and “MD pattern  148 .” In some embodiments, each of the MD patterns  144 - 148  may electrically couple the source or drain feature of a corresponding transistor to one or more upper-level interconnect structures, which will be discussed in further detail below. As a non-limiting example, the MD pattern  144  can electrically couple the source/drain feature (e.g., formed by the portion  124 ) to an upper-level interconnect structure. 
     The layout design  100  further includes a pattern  150 . The pattern  150  is configured to form a via interconnect structure (e.g., VD), hereinafter “VD pattern  150 .” The via interconnect structure formed by the VD pattern  150  may extend along a vertical direction (e.g., a direction perpendicular to the X axis and the Y axis) with a height in order to electrically couple a corresponding MD (e.g., formed by the MD pattern  144 ) to an upper-level interconnect structure. The layout design  100  further includes a pattern  152 . The pattern  152  is configured to form a via interconnect structure (e.g., VG), hereinafter “VG pattern  152 .” The via interconeect structure formed by the VG pattern  152  may extend along a vertical direction (e.g., a direction perpendicular to the X axis and the Y axis) with a height in order to electrically couple a corresponding gate structure (e.g., formed by the gate structure pattern  104 ) to an upper-level interconnect structure. 
     According to various embodiments of the present disclosure, the features of the transistors (e.g., gate features  104 - 114 , source/drain features  120 - 134 ) are referred to as being formed in a front-end-of-line (FEOL) layer. The interconnect structures formed by the MD patterns  142 - 148 , VD pattern  150 , and VG pattern  152  are referred to as being formed in a middle-end-of-line (MEOL) layer, which is disposed above the FEOL layer. Further above the MEOL layer, a number of back-end-of-line (BEOL) layers (e.g., about  10 ) can be formed. Each BEOL layer can include a number of interconnect structures to electrically couple the transistors. 
     For example, the layout design  100  further includes patterns  154 ,  156 ,  158 , and  160 . The patterns  154  to  160  may extend along the first lateral direction (e.g., the X axis of  FIG. 1 ). Although the patterns  154 - 160  are each shown as a segmental pattern in the example of  FIG. 1 , it should be understood that the layout design  100  can include any number of other similar patterns but continuously extending along the whole (active region) pattern  102  based on functionality of the completed semiconductor device, while remaining within the scope of the present disclosure. The patterns  154  to  160  are each configured to form an interconnect structure at the bottommost one of the BEOL layers (e.g., M 0 ), hereinafter “M 0  pattern  154 ,” “M 0  pattern  156 ,” “M 0  pattern  158 ,” and “M 0  pattern  160 ,” respectively. In accordance with various embodiments, the interconnect structures in the BEOL layers formed by some of the M 0  patterns  154  to  160  can overlay at least one structure/feature in the FEOL or MEOL layer (with the respective patterns overlapped with each other) to form the disclosed interlayer decoupling capacitors, which will be discussed in further detail below. 
     Referring next to  FIG. 2A , illustrated in a perspective view of a semiconductor device  200  that can be fabricated based on the layout deign  100  of  FIG. 1  to include a number of interlayer decoupling capacitors, in accordance with various embodiments. Correspondence between the layout design  100  and the semiconductor device  200  will be further illustrated through the following discussion. In the example of  FIG. 2A , the semiconductor device  200  may include additional structures formed by patterns not shown in the layout design  100 . For purposes of clarification,  FIG. 2B  further illustrates a cross-sectional view of a portion of the semiconductor device  200  (e.g., one of the DCAP areas), cut along cross-section X-X indicated in  FIG. 2A . 
     In some embodiments, the semiconductor device  200  is formed as a FinFET device in the illustrated example of  FIGS. 2A-B . However, it should be appreciated that the semiconductor device  200  may be formed as any of various other non-planer transistor devices (e.g., a GAA transistor device) or a planar transistor device based on the layout design  100  of  FIG. 1 , while remaining within the scope of the present disclosure. 
     As shown, the semiconductor device  200  includes a substrate  202 , and a fin structure  204  protruding from a major surface of the substrate  202 . The fin structure  204  may be formed based on the active region pattern  102  of  FIG. 1  to extend along the X axis. On opposite sides of the fin structure  204  (along the Y axis), a shallow trench isolation (STI) structure  205  may be formed over the major surface of the substrate  202  to embed a lower portion of the fins structure  204 . The semiconductor device  200  further includes (e.g., metal) gate structures,  206 ,  208 ,  210 ,  212 ,  214 , and  216 , straddling a number of portions of the fin structure  204 . The gate structures  206 ,  208 ,  210 ,  212 ,  214 , and  216  may be formed based on the gate structure patterns  104 ,  106 ,  108 ,  110 ,  112 , and  114  of  FIG. 1 , respectively, to each extend along the Y axis. Along the fin structure  204  next to opposite sides of each gate structure, the semiconductor device  200  further includes (e.g., epitaxially grown) source/drain structures,  218 ,  220 ,  222 ,  224 ,  226 ,  228 ,  230 , and  232 , which may be formed based on the portions  120 ,  122 ,  124 ,  126 ,  128 ,  130 ,  132 , and  134  of  FIG. 1 , respectively. The gate structures  206  to  216  and source/drain structures  218  to  232  are sometimes referred to as being part of the FEOL layer, as indicated in  FIG. 2B . 
     In some embodiments, the fin structure  204  may be formed as a continuous structure with a number of gate structures crossing thereon. As such, the semiconductor device  200  can have a number of active circuits and a number of decoupling capacitors sharing the same active region (e.g., the fin structure  204 ). For example in  FIG. 1 , the gate structures  210  to  212 , together with corresponding portions of the fin structure  204  (e.g.,  224 ,  226 , etc.), may form a number of active circuits (e.g., a memory circuit, a logic circuit, an input/output circuit, etc.) in the active circuit area, while the gate structures  206  to  208  and  214  to  216 , together with corresponding portions of the fin structure  204  (e.g.,  218 ,  220 ,  222 ,  228 ,  230 ,  232 , etc.), may at least in part form a number of decoupling capacitors in the DCAP area(s). Further, the gate structures to form the disclosed decoupling capacitors may be disposed closer to the edge of the fin structure  204  than the gate structures to form the active circuits, according to various embodiments. Alternatively stated, along a same active region where active circuits and decoupling capacitors are concurrently formed, the decoupling capacitors are disposed on the sides of the active region, with the active circuits sandwiched between the decoupling capacitors. 
     Coupled to the source/drain structure  222 , the semiconductor device  200  further includes an interconnect structure (e.g., MD)  234 , which may be formed based on the MD pattern  144 . The MD  234  can extend along the Y axis. Coupled to the MD  234 , the semiconductor device  200  further includes an interconnect structure (e.g., VD)  236 , which may be formed based on the VD pattern  150 . The VD  236  can extend along a vertical direction (e.g., the Z axis of  FIG. 2A ). Coupled to the gate structure  206 , the semiconductor device  200  further includes a via interconnect structure (e.g., VG)  238 , which may be formed based on the VG pattern  152 . The VG  238  can extend along the Z axis. The MD  242 , VD  236 , and VG  238  are sometimes referred to as being part of the MEOL layer, as indicated in  FIG. 2B . 
     Over the MEOL layer, the semiconductor device  200  further includes a number of BEOL layers (sometimes referred to as metallization layers), each of which includes a number of interconnect structures. In the illustrated embodiments of  FIGS. 2A-B , the bottommost BEOL layer (sometimes referred to as an M 0  layer) includes interconnect structures (e.g., M 0 )  240 ,  242 ,  244 , and  246 . The M 0 &#39;s  240 ,  242 ,  244 , and  246  may be formed based on the M 0  patterns  154 ,  156 ,  158 , and  160  of  FIG. 1  to extend along the X axis. 
     According to various embodiments of the present disclosure, the M 0   240  can be vertically disposed over the gate structure  206  with an interlayer dielectric (ILD) disposed therebetween to form a first interlayer decoupling capacitor, C 1 . The M 0   240  and gate structure  206  can function as opposite electrodes (terminals or otherwise ends) of the first interlayer decoupling capacitor, C 1 , respectively. The M 0   242  can be vertically disposed over the MD  234  with an ILD disposed therebetween to form a second interlayer decoupling capacitor, C 2 . The M 0   242  and MD  234  can function as opposite electrodes (terminals or otherwise ends) of the second interlayer decoupling capacitor, C 2 , respectively. The M 0   242  can laterally extend with a certain distance to overlay a portion of the source/drain structure  222  so as to form a third interlayer decoupling capacitor, C 3 . The M 0   242  and source/drain structure  222  can function as opposite electrodes (terminals or otherwise ends) of the third interlayer decoupling capacitor, C 3 , respectively. 
     A capacitance value of each of the disclosed decoupling capacitors, C 1  to C 3 , may be determined based on various parameters of its electrodes and the dielectric layer interposed therebetween, in accordance with various embodiments. For example, the capacitance value of the decoupling capacitor C 1  may be determined based on at least one of: (i) how much in area the M 0   240  and gate structure  206  overlap with each other (when viewed from the top); (ii) a vertical distance between the M 0   240  and gate structure  206 : or (iii) a dielectric contact of the ILD interposed between the M 0   240  and gate structure  206 . In another example, the capacitance value of the decoupling capacitor C 2  may be determined based on at least one of: (i) how much in area the M 0   242  and MD  234  overlap with each other (when viewed from the top); (ii) a vertical distance between the M 0   242  and MD  234 : or (iii) a dielectric contact of the ILD interposed between the M 0   242  and MD  234 . In yet another example, capacitance value of the decoupling capacitor C 3  may be determined based on at least one of: (i) how much in area the M 0   242  and the portion of the source/drain structure  222  overlap with each other (when viewed from the top); (ii) a vertical distance between the M 0   242  and the source/drain structure  222 : or (iii) a dielectric contact of the ILD interposed between the M 0   242  and the source/drain structure  222 . 
     Although not shown, the semiconductor device  200  may include one or more other interlayer decoupling capacitors formed by a region of the substrate  202  that is not overlaid by the STI structure  205  and one of the M 0 &#39;s. Alternatively stated, the region of the substrate  202  and the M 0  can function as opposite electrodes (terminals or otherwise ends) of this type of interlayer decoupling capacitors, respectively. Such a region can have a conduction type, for example, a p-type doped region or an n-type doped region. 
     Further, the M 0   244  can be laterally disposed next to the M 0   240  with an intralayer metal dielectric (IMD) disposed therebetween to form a first intralayer decoupling capacitor, C 4 . The M 0 &#39;s  240  and  244  can function as opposite electrodes (terminals or otherwise ends) of the first intralayer decoupling capacitor, C 4 , respectively. The M 0   246  can be laterally disposed next to the M 0   242  with an IMD disposed therebetween to form a second intralayer decoupling capacitor, C 5 . The M 0 &#39;s  242  and  246  can function as opposite electrodes (terminals or otherwise ends) of the second intralayer decoupling capacitor, C 5 , respectively. 
     Over the M 0  layer, the semiconductor device  200  further includes a number of BEOL layers, for example, an M 1  layer and up to the topmost MX layer, as shown in  FIG. 2B . In the M 1  layer, the semiconductor device  200  further includes a number of interconnect structures (e.g., M 1 )  252  and  254 , extending along the Y axis. In the illustrated example of  FIG. 2A , the M 1   252  is electrically coupled to the M 0   244  through a via interconnect structure  248 , and the M 1   254  is electrically coupled to the M 0   246  through a via interconnect structure  250 . Over the M 1  layer, the semiconductor device  200  further includes a number of BEOL layers. Each of such BEOL layers can include a number of interconnect structures, extending either along the X axis or the Y axis, to electrically couple the lower-level interconnect structures to the higher-level interconnect structures. For example, the semiconductor device  200  can include a number of interconnect structures (not shown) between the M 1  layer and the topmost MX layer to electrically couple the M 1 &#39;s  252  and  254  to a power rail  260  in the topmost MX layer. The power rail  260  can provide a power supply voltage, e.g., VDD, VSS. 
     According to various embodiments of the present disclosure, each of the interlayer decoupling capacitors (C 1 , C 2 , C 3 ) and intralayer decoupling capacitors (C 4 , C 5 ) has one electrode electrically tied to either VDD or VSS, and the other electrode connected to a decoupling node, which may be the input of a circuit formed by the transistors in the active circuit area. As such, each of the interlayer/intralayer decoupling capacitors can help smooth out any unexpected changes in an input voltage (to the corresponding circuit) from a power supply. 
     For example, the interlayer decoupling capacitor C 1  has one of its electrodes (e.g., the gate structure  206 ) coupled to the power rail  260  carrying VDD or VSS through the VG  238 , the M 0   244  and a number of interconnect structures therebetween (e.g.,  248 ,  252 , etc.), and the other one of its electrodes (e.g., the M 0   240 ) connected to a circuit (not shown) in the active circuit area. The interlayer decoupling capacitor C 2  has one of its electrodes (e.g., the MD  234 ) coupled to the power rail  260  carrying VDD or VSS through the VD  236 , the M 0   246  and a number of interconnect structures therebetween (e.g.,  250 ,  254 , etc.), and the other one of its electrodes (e.g., the M 0   242 ) connected to a circuit (not shown) in the active circuit area. The interlayer decoupling capacitor C 3  has one of its electrodes (e.g., the source/drain structure  222 ) coupled to the power rail  260  carrying VDD or VSS through the MD  234 , the VD  236 , the M 0   246  and a number of interconnect structures therebetween (e.g.,  250 ,  254 , etc.), and the other one of its electrodes (e.g., the M 0   242 ) connected to a circuit (not shown) in the active circuit area. The intralayer decoupling capacitor C 4  has one of its electrodes (e.g., the M 0   244 ) coupled to the power rail  260  carrying VDD or VSS through a number of interconnect structures therebetween (e.g.,  248 ,  252 , etc.), and the other one of its electrodes (e.g., the M 0   240 ) connected to a circuit (not shown) in the active circuit area. The intralayer decoupling capacitor C 5  has one of its electrodes (e.g., the M 0   246 ) coupled to the power rail  260  carrying VDD or VSS through a number of interconnect structures therebetween (e.g.,  250 ,  254 , etc.), and the other one of its electrodes (e.g., the M 0   242 ) connected to a circuit (not shown) in the active circuit area. 
       FIG. 3  is a flowchart of a method  300  of forming or manufacturing a semiconductor device, in accordance with some embodiments. It is understood that additional operations may be performed before, during, and/or after the method  300  depicted in  FIG. 3 . In some embodiments, the method  300  is usable to form a semiconductor device, according to various layout designs as disclosed herein. 
     In operation  310  of the method  300 , a layout design of a semiconductor device (e.g., the layout design  100  of  FIG. 1 ) is generated. The operation  310  is performed by a processing device (e.g., processor  402  of  FIG. 4 ) configured to execute instructions for generating a layout design. In one approach, the layout design is generated by placing layout designs of one or more standard cells through a user interface. In one approach, the layout design is automatically generated by a processor executing a synthesis tool that converts a logic design (e.g., Verilog) into a corresponding layout design. In some embodiments, the layout design is rendered in a graphic database system (GDSII) file format. 
     In operation  320  of the method  300 , a semiconductor device is manufactured based on the layout design. In some embodiments, the operation  320  of the method  300  includes manufacturing at least one mask based on the layout design, and manufacturing the a semiconductor device based on the at least one mask. A number of example manufacturing operations of the operation  320  will be discussed with respect to the method  600  of  FIG. 6  below. 
       FIG. 4  is a schematic view of a system  400  for designing and manufacturing an IC layout design, in accordance with some embodiments. The system  400  generates or places one or more IC layout designs, as described herein. In some embodiments, the system  400  manufactures one or more semiconductor devices based on the one or more IC layout designs, as described herein. The system  400  includes a hardware processor  402  and a non-transitory, computer readable storage medium  404  encoded with, e.g., storing, the computer program code  406 , e.g., a set of executable instructions. The computer readable storage medium  404  is configured for interfacing with manufacturing machines for producing the semiconductor device. The processor  402  is electrically coupled to the computer readable storage medium  404  by a bus  408 . The processor  402  is also electrically coupled to an I/O interface  410  by the bus  408 . A network interface  412  is also electrically connected to the processor  402  by the bus  408 . Network interface  412  is connected to a network  414 , so that the processor  402  and the computer readable storage medium  404  are capable of connecting to external elements via network  414 . The processor  402  is configured to execute the computer program code  406  encoded in the computer readable storage medium  404  in order to cause the system  400  to be usable for performing a portion or all of the operations as described in method  300 . 
     In some embodiments, the processor  402  is a central processing unit (CPU), a multi-processor, a distributed processing system, an application specific integrated circuit (ASIC), and/or a suitable processing unit. 
     In some embodiments, the computer readable storage medium  404  is an electronic, magnetic, optical, electromagnetic, infrared, and/or a semiconductor system (or apparatus or device). For example, the computer readable storage medium  404  includes a semiconductor or solid-state memory, a magnetic tape, a removable computer diskette, a random access memory (RAM), a read-only memory (ROM), a rigid magnetic disk, and/or an optical disk. In some embodiments using optical disks, the computer readable storage medium  404  includes a compact disk-read only memory (CD-ROM), a compact disk-read/write (CD-R/W), and/or a digital video disc (DVD). 
     In some embodiments, the storage medium  404  stores the computer program code  406  configured to cause the system  400  to perform the method  300 . In some embodiments, the storage medium  404  also stores information needed for performing method  300  as well as information generated during performance of method  300 , such as layout design  416 , user interface  418 , fabrication unit  420 , and/or a set of executable instructions to perform the operation of method  300 . 
     In some embodiments, the storage medium  404  stores instructions (e.g., the computer program code  406 ) for interfacing with manufacturing machines. The instructions (e.g., the computer program code  406 ) enable the processor  402  to generate manufacturing instructions readable by the manufacturing machines to effectively implement the method  300  during a manufacturing process. 
     The system  400  includes the I/O interface  410 . The I/O interface  410  is coupled to external circuitry. In some embodiments, the I/O interface  410  includes a keyboard, keypad, mouse, trackball, trackpad, and/or cursor direction keys for communicating information and commands to the processor  402 . 
     The system  400  also includes the network interface  412  coupled to the processor  402 . The network interface  412  allows the system  400  to communicate with the network  414 , to which one or more other computer systems are connected. The network interface  412  includes wireless network interfaces such as BLUETOOTH, WIFI, WIMAX, GPRS, or WCDMA; or wired network interface such as ETHERNET, USB, or IEEE-13154. In some embodiments, the method  300  is implemented in two or more systems  400 , and information such as layout design, user interface and fabrication unit are exchanged between different systems  400  by the network  414 . 
     The system  400  is configured to receive information related to a layout design through the I/O interface  410  or network interface  412 . The information is transferred to the processor  402  by the bus  408  to determine a layout design for producing an IC. The layout design is then stored in the computer readable medium  404  as the layout design  416 . The system  400  is configured to receive information related to a user interface through the I/O interface  410  or network interface  412 . The information is stored in the computer readable medium  404  as the user interface  418 . The system  400  is configured to receive information related to a fabrication unit through the I/O interface  410  or network interface  412 . The information is stored in the computer readable medium  404  as the fabrication unit  420 . In some embodiments, the fabrication unit  420  includes fabrication information utilized by the system  400 . 
     In some embodiments, the method  300  is implemented as a standalone software application for execution by a processor. In some embodiments, the method  300  is implemented as a software application that is a part of an additional software application. In some embodiments, the method  300  is implemented as a plug-in to a software application. In some embodiments, the method  300  is implemented as a software application that is a portion of an EDA tool. In some embodiments, the method  300  is implemented as a software application that is used by an EDA tool. In some embodiments, the EDA tool is used to generate a layout design of the integrated circuit device. In some embodiments, the layout design is stored on a non-transitory computer readable medium. In some embodiments, the layout design is generated using a tool such as VIRTUOSO® available from CADENCE DESIGN SYSTEMS, Inc., or another suitable layout generating tool. In some embodiments, the layout design is generated based on a netlist which is created based on the schematic design. In some embodiments, the method  300  is implemented by a manufacturing device to manufacture an integrated circuit using a set of masks manufactured based on one or more layout designs generated by the system  400 . In some embodiments, the system  400  includes a manufacturing device (e.g., fabrication tool  422 ) to manufacture an integrated circuit using a set of masks manufactured based on one or more layout designs of the present disclosure. In some embodiments, the system  400  of  FIG. 4  generates layout designs of an IC that are smaller than other approaches. In some embodiments, the system  400  of  FIG. 4  generates layout designs of a semiconductor device that occupy less area than other approaches. 
       FIG. 5  is a block diagram of an integrated circuit (IC)/semiconductor device manufacturing system  500 , and an IC manufacturing flow associated therewith, in accordance with at least one embodiment of the present disclosure. 
     In  FIG. 5 , the IC manufacturing system  500  includes entities, such as a design house  520 , a mask house  530 , and an IC manufacturer/fabricator (“fab”)  540 , that interact with one another in the design, development, and manufacturing cycles and/or services related to manufacturing an IC device (semiconductor device)  560 . The entities in system  500  are connected by a communications network. In some embodiments, the communications network is a single network. In some embodiments, the communications network is a variety of different networks, such as an intranet and the Internet. The communications network includes wired and/or wireless communication channels. Each entity interacts with one or more of the other entities and provides services to and/or receives services from one or more of the other entities. In some embodiments, two or more of design house  520 , mask house  530 , and IC fab  540  is owned by a single company. In some embodiments, two or more of design house  520 , mask house  530 , and IC fab  540  coexist in a common facility and use common resources. 
     The design house (or design team)  520  generates an IC design layout  522 . The IC design layout  522  includes various geometrical patterns designed for the IC device  560 . The geometrical patterns correspond to patterns of metal, oxide, or semiconductor layers that make up the various components of the IC device  560  to be fabricated. The various layers combine to form various IC features. For example, a portion of the IC design layout  522  includes various IC features, such as an active region (e.g.,  204  of  FIG. 2 ), gate structures (e.g.,  206 - 216  of  FIG. 2 ), source/drain structures (e.g.,  218 - 232  of  FIG. 2 ), interconnect structures (e.g.,  234 - 254  of  FIG. 2 ), and openings for bonding pads, to be formed in a semiconductor substrate (such as a silicon wafer) and various material layers disposed on the semiconductor substrate. The design house  520  implements a proper design procedure to form the IC design layout  522 . The design procedure includes one or more of logic design, physical design or place and route. The IC design layout  522  is presented in one or more data files having information of the geometrical patterns. For example, the IC design layout  522  can be expressed in a GDSII file format or DFII file format. 
     The mask house  530  includes mask data preparation  532  and mask fabrication  534 . The mask house  530  uses the IC design layout  522  to manufacture one or more masks to be used for fabricating the various layers of the IC device  560  according to the IC design layout  522 . The mask house  530  performs the mask data preparation  532 , where the IC design layout  522  is translated into a representative data file (“RDF”). The mask data preparation  532  provides the RDF to the mask fabrication  534 . The mask fabrication  534  includes a mask writer. A mask writer converts the RDF to an image on a substrate, such as a mask (reticle) or a semiconductor wafer. The design layout is manipulated by the mask data preparation  532  to comply with particular characteristics of the mask writer and/or requirements of the IC fab  540 . In  FIG. 5 , the mask data preparation  532  and mask fabrication  534  are illustrated as separate elements. In some embodiments, the mask data preparation  532  and mask fabrication  534  can be collectively referred to as mask data preparation. 
     In some embodiments, the mask data preparation  532  includes optical proximity correction (OPC) which uses lithography enhancement techniques to compensate for image errors, such as those that can arise from diffraction, interference, other process effects and the like. OPC adjusts the IC design layout  522 . In some embodiments, the mask data preparation  532  includes further resolution enhancement techniques (RET), such as off-axis illumination, sub-resolution assist features, phase-shifting masks, other suitable techniques, and the like or combinations thereof. In some embodiments, inverse lithography technology (ILT) is also used, which treats OPC as an inverse imaging problem. 
     In some embodiments, the mask data preparation  532  includes a mask rule checker (MRC) that checks the IC design layout that has undergone processes in OPC with a set of mask creation rules which contain certain geometric and/or connectivity restrictions to ensure sufficient margins, to account for variability in semiconductor manufacturing processes, and the like. In some embodiments, the MRC modifies the IC design layout to compensate for limitations during the mask fabrication  534 , which may undo part of the modifications performed by OPC in order to meet mask creation rules. 
     In some embodiments, the mask data preparation  532  includes lithography process checking (LPC) that simulates processing that will be implemented by the IC fab  540  to fabricate the IC device  560 . LPC simulates this processing based on the IC design layout  522  to create a simulated manufactured device, such as the IC device  560 . The processing parameters in LPC simulation can include parameters associated with various processes of the IC manufacturing cycle, parameters associated with tools used for manufacturing the IC, and/or other aspects of the manufacturing process. LPC takes into account various factors, such as aerial image contrast, depth of focus (“DOF”), mask error enhancement factor (“MEEF”), other suitable factors, and the like or combinations thereof. In some embodiments, after a simulated manufactured device has been created by LPC, if the simulated device is not close enough in shape to satisfy design rules, OPC and/or MRC can be repeated to further refine the IC design layout  522 . 
     It should be understood that the above description of the mask data preparation  532  has been simplified for the purposes of clarity. In some embodiments, the mask data preparation  532  includes additional features such as a logic operation (LOP) to modify the IC design layout according to manufacturing rules. Additionally, the processes applied to the IC design layout  522  during the mask data preparation  532  may be executed in a variety of different orders. 
     After the mask data preparation  532  and during mask fabrication  534 , a mask or a group of masks are fabricated based on the modified IC design layout. In some embodiments, an electron-beam (e-beam) or a mechanism of multiple e-beams is used to form a pattern on a mask (photomask or reticle) based on the modified IC design layout. The mask can be formed in various technologies. In some embodiments, the mask is formed using binary technology. In some embodiments, a mask pattern includes opaque regions and transparent regions. A radiation beam, such as an ultraviolet (UV) beam, used to expose the image sensitive material layer (e.g., photoresist) which has been coated on a wafer, is blocked by the opaque region and transmits through the transparent regions. In one example, a binary mask includes a transparent substrate (e.g., fused quartz) and an opaque material (e.g., chromium) coated in the opaque regions of the mask. In another example, the mask is formed using a phase shift technology. In the phase shift mask (PSM), various features in the pattern formed on the mask are configured to have proper phase difference to enhance the resolution and imaging quality. In various examples, the phase shift mask can be attenuated PSM or alternating PSM. The mask(s) generated by the mask fabrication  534  is used in a variety of processes. For example, such a mask(s) is used in an ion implantation process to form various doped regions in the semiconductor wafer, in an etching process to form various etching regions in the semiconductor wafer, and/or in other suitable processes. 
     The IC fab  540  is an IC fabrication entity that includes one or more manufacturing facilities for the fabrication of a variety of different IC products. In some embodiments, the IC fab  540  is a semiconductor foundry. For example, there may be a first manufacturing facility for the front end fabrication of a plurality of IC products (e.g., a front-end-of-line (FEOL) layer), while a second manufacturing facility may provide the middle end fabrication for the interconnection of the IC products (e.g., a middle-end-of-line (MEOL) layer) and a third manufacturing facility may provide the back end fabrication for the interconnection and packaging of the IC products (e.g., a back-end-of-line (BEOL) layer), and a fourth manufacturing facility may provide other services for the foundry entity. 
     The IC fab  540  uses the mask (or masks) fabricated by the mask house  530  to fabricate the IC device  560 . Thus, the IC fab  540  at least indirectly uses the IC design layout  522  to fabricate the IC device  560 . In some embodiments, a semiconductor wafer  542  is fabricated by the IC fab  540  using the mask (or masks) to form the IC device  560 . The semiconductor wafer  542  includes a silicon substrate or other proper substrate having material layers formed thereon. Semiconductor wafer further includes one or more of various doped regions, dielectric features, multilevel interconnects, and the like (formed at subsequent manufacturing steps). 
     The system  500  is shown as having the design house  520 , mask house  530 , and IC fab  540  as separate components or entities. However, it should be understood that one or more of the design house  520 , mask house  530  or IC fab  540  are part of the same component or entity. 
       FIG. 6  is a flowchart illustrating an example method  600  for fabricating a semiconductor device  700  that includes the disclosed interlayer decoupling capacitors, according to various aspects of the present disclosure. The method  600  may be part of the operation  320  of the method  300  ( FIG. 3 ). As such, the semiconductor device  700  may be made based on at least a portion of the layout design disclosed herein. For example, the layout design  100  of  FIG. 1  may be used to make the semiconductor device  700 . Thus, the semiconductor device  200  of  FIGS. 2A-B  (made out of the layout design  100 ) may share some substantially similar features/structures as the semiconductor device  700 . 
       FIGS. 7, 8, 9, 10, 11, and 12  show schematic cross-sectional views of the semiconductor device  700  at various stages of fabrication, according to an embodiment of the method  600  of  FIG. 6 . Thus, each of the operations of the method  600  shall be discussed in conjunction with a corresponding one of the cross-sectional views of the semiconductor device  700  shown in  FIGS. 7-12 . 
     The semiconductor device  700  may include a microprocessor, memory cell, and/or other integrated circuits (ICs). It is noted that the method of  FIG. 6  does not produce a completed semiconductor device  700 . A completed semiconductor device  700  may be fabricated using complementary metal-oxide-semiconductor (CMOS) technology processing. Accordingly, it is understood that additional operations may be provided before, during, and after the method  600  of  FIG. 6 , and that some other operations may only be briefly described herein. Also,  FIGS. 7 through 12  are simplified for a better understanding of the present disclosure. For example, although the figures illustrate the semiconductor device  700 , it is understood the semiconductor device  700  may include a number of other devices comprising transistors, resistors, capacitors, inductors, fuses, etc. 
     Referring to  FIGS. 6 and 7 , the method  600  begins at operation  602  in which at least an active region  704  is formed over a substrate  702 , in accordance with some embodiments. The cross-sectional view of semiconductor device  700  shown in  FIG. 7  may be cut along a lengthwise direction of the active region  704  (e.g., the X axis indicated in  FIG. 2A ). 
     The substrate  702  may be a semiconductor substrate, such as a bulk semiconductor, a semiconductor-on-insulator (SOI) substrate, or the like, which may be doped (e.g., with a p-type or an n-type dopant) or undoped. The substrate  702  may be a wafer, such as a silicon wafer. Generally, an SOI substrate includes a layer of a semiconductor material formed on an insulator layer. The insulator layer may be, for example, a buried oxide (BOX) layer, a silicon oxide layer, or the like. The insulator layer is provided on a substrate, typically a silicon or glass substrate. Other substrates, such as a multi-layered or gradient substrate may also be used. In some embodiments, the semiconductor material of the substrate  702  may include silicon; germanium; a compound semiconductor including silicon carbide, gallium arsenic, gallium phosphide, indium phosphide, indium arsenide, and/or indium antimonide; an alloy semiconductor including SiGe, GaAsP, AlInAs, AlGaAs, GaInAs, GaInP, and/or GaInAsP; or combinations thereof. 
     In some embodiments, the active region  704  is formed as a fin structure (hereinafter “fin  704 ”) that extends along the X axis, i.e., having a lengthwise direction along the X axis. Although in the illustrated example of  FIG. 7 , the fin  704  is shown as a portion protruding from a major surface (indicated by dotted line) of the substrate  702 . While remaining within the scope of the present disclosure, however, it should be understood that the active region  704  can be formed as a stack structure that also protrudes from the major surface of the substrate  702 , but includes a number of first semiconductor layers (functioning as channel layers) and a number of second semiconductor layers (function as sacrificial layers) alternatively stacked on top of one another. 
     Although one fin is shown in the illustrated embodiment of  FIG. 7  (and the following figures), it should be appreciated that the semiconductor device  700  can include any number of fins while remaining within the scope of the present disclosure. In some embodiments, the fin  704  is formed by patterning the substrate  702  using, for example, photolithography and etching techniques. For example, a mask layer, such as a pad oxide layer and an overlying pad nitride layer, is formed over the substrate  702 . The pad oxide layer may be a thin film comprising silicon oxide formed, for example, using a thermal oxidation process. The pad oxide layer may act as an adhesion layer between the substrate  702  and the overlying pad nitride layer. In some embodiments, the pad nitride layer is formed of silicon nitride, silicon oxynitride, silicon carbonitride, the like, or combinations thereof. The pad nitride layer may be formed using low-pressure chemical vapor deposition (LPCVD) or plasma enhanced chemical vapor deposition (PECVD), for example. 
     The mask layer may be patterned using photolithography techniques. Generally, photolithography techniques utilize a photoresist material (not shown) that is deposited, irradiated (exposed), and developed to remove a portion of the photoresist material. The remaining photoresist material protects the underlying material, such as the mask layer in this example, from subsequent processing steps, such as etching. For example, the photoresist material is used to pattern the pad oxide layer and pad nitride layer to form a patterned mask. 
     The patterned mask is subsequently used to pattern exposed portions of the substrate  702  to form trenches (or openings), thereby defining a fin structure (e.g.,  704 ) between adjacent trenches. When multiple fin structures are formed, such a trench may be disposed between any adjacent ones of the fin structures. In some embodiments, the fin  704  is formed by etching trenches in the substrate  702  using, for example, reactive ion etch (RIE), neutral beam etch (NBE), the like, or combinations thereof. The etch may be anisotropic. In some embodiments, the trenches may be strips (viewed from the top) parallel to each other, and closely spaced with respect to each other. In some embodiments, the trenches may be continuous and surround each of the fins. 
     The fin  704  may be patterned by any suitable method. For example, the fin  704  may be patterned using one or more photolithography processes, including double-patterning or multi-patterning processes. Generally, double-patterning or multi-patterning processes combine photolithography and self-aligned processes, allowing patterns to be created that have, for example, pitches smaller than what is otherwise obtainable using a single, direct photolithography process. For example, in one embodiment, a sacrificial layer is formed over a substrate and patterned using a photolithography process. Spacers are formed alongside the patterned sacrificial layer using a self-aligned process. The sacrificial layer is then removed, and the remaining spacers, or mandrels, may then be used to pattern the fin. 
     Referring to  FIGS. 6 and 8 , the method  600  proceeds to operation  604  in which a number of dummy gate structures  802 ,  804 ,  806 ,  808 ,  810 , and  812  are formed, in accordance with some embodiments. The cross-sectional view of semiconductor device  700  shown in  FIG. 8  may be cut along a lengthwise direction of the active region  704  (e.g., the X axis indicated in  FIG. 2A ). 
     The dummy gate structures  802  to  812  are each formed to straddle a respective portion of the fins  704 . For example, each of the dummy gate structures  802  to  812  may extend along a direction perpendicular to the lengthwise direction of the fin  704  (e.g., the Y axis indicated in  FIG. 2A ). Further, some of the dummy gate structures (e.g.,  802 - 804 ,  810 - 812 ) are disposed in an area closer to the edge of the fin  704  (e.g.,  704 A) than an area farther from the edge of the fin  704  (e.g.,  704 B) where other dummy gate structures (e.g.,  806 - 808 ) are disposed. 
     The dummy gate structures  802  to  812  can each include a dummy gate dielectric and a dummy gate, in some embodiments. To form the dummy gate structures  802  to  812 , a dielectric layer is formed on the fin  704 . The dielectric layer may be, for example, silicon oxide, silicon nitride, multilayers thereof, or the like, and may be deposited or thermally grown. 
     A gate layer is formed over the dielectric layer, and a mask layer is formed over the gate layer. The gate layer may be deposited over the dielectric layer and then planarized, such as by a CMP. A mask layer may be deposited over the gate layer. The gate layer may be formed of, for example, polysilicon, although other materials may also be used. The mask layer may be formed of, for example, silicon nitride or the like. 
     After the layers (e.g., the dielectric layer, the gate layer, and the mask layer) are formed, the mask layer may be patterned using acceptable photolithography and etching techniques. The pattern of the mask may then be transferred to the gate layer and the dielectric layer by an acceptable etching technique to form the dummy gate and the underlying dummy gate dielectric of each of the dummy gate structures  802  to  812 . The dummy gate and the dummy gate dielectric collectively cover a portion (e.g., a channel region) of the fin  704 . 
     Referring to  FIGS. 6 and 9 , the method  600  proceeds to operation  606  in which a number of source/drain structures  902 ,  904 ,  906 ,  908 ,  910 ,  912 ,  914 , and  916  are formed, in accordance with some embodiments. The cross-sectional view of semiconductor device  700  shown in  FIG. 9  may be cut along a lengthwise direction of the active region  704  (e.g., the X axis indicated in  FIG. 2A ). 
     Upon forming the dummy gate structures  802  to  812 , gate spacers (not shown) may be formed on opposite sides (along the X axis) of each of the dummy gate structures  802  to  812 . The gate spacer may be a low-k spacer and may be formed of a suitable dielectric material, such as silicon oxide, silicon oxycarbonitride, or the like. Any suitable deposition method, such as thermal oxidation, chemical vapor deposition (CVD), or the like, may be used to form the gate spacer. 
     The source/drain structures  902 ,  904 ,  906 ,  908 ,  910 ,  912 ,  914 , and  916  are formed in recesses of the semiconductor fin structure  704  next to the dummy gate structures, e.g., between adjacent dummy gate structures (e.g., between the dummy gate structures  804  and  806 ) and/or next to a dummy gate structure (e.g., next to the dummy gate structure  802 ). The recesses are formed by, e.g., an anisotropic etching process using the dummy gate structures and corresponding gate spacers as an etching mask, in some embodiments, although any other suitable etching process may also be used. 
     The source/drain structures  902  to  916  are formed by epitaxially growing a semiconductor material in the recess, using suitable methods such as metal-organic CVD (MOCVD), molecular beam epitaxy (MBE), liquid phase epitaxy (LPE), vapor phase epitaxy (VPE), selective epitaxial growth (SEG), the like, or a combination thereof 
     The epitaxial source/drain structures  902  to  916  may have surfaces raised from respective surfaces of the semiconductor fin  704  (e.g. raised above the non-recessed portions of the semiconductor fin  704 ) and may have facets. In some embodiments, when the resulting transistor is an n-type transistor, the source/drain structures  902  to  916  can include silicon carbide (SiC), silicon phosphorous (SiP), phosphorous-doped silicon carbon (SiCP), or the like. In some embodiments, when the resulting transistor is a p-type transistor, the source/drain structures  902  to  916  can include SiGe, and a p-type impurity such as boron or indium. 
     The epitaxial source/drain structures  902  to  916  may be implanted with dopants, followed by an annealing process. The implanting process may include forming and patterning masks such as a photoresist to cover the regions of the workpiece that are to be protected from the implanting process. The source/drain structures  902  to  916  may have an impurity (e.g., dopant) concentration in a range from about 1×10 19  cm −3  to about 1×10 21  cm −3 . P-type impurities, such as boron or indium, may be implanted in the source/drain structures  1200  of a P-type transistor. N-type impurities, such as phosphorous or arsenide, may be implanted in the source/drain structures  902  to  916  of an N-type transistor. In some embodiments, the epitaxial source/drain structures  902  to  916  may be in situ doped during their growth. 
     Upon forming the source/drain structures  902  to  916 , an interlayer dielectric (ILD)  920  is formed over the source/drain structures  902  to  916 . The ILD  920  is formed of a dielectric material such as silicon oxide, phosphosilicate glass (PSG), borosilicate glass (BSG), boron-doped phosphosilicate Glass (BPSG), undoped silicate glass (USG), or the like, and may be deposited by any suitable method, such as CVD, PECVD, or FCVD. After the ILD  920  is formed, an optional dielectric layer can be formed over the ILD  920 . The dielectric layer can function as a protection layer to prevent or reduces the loss of the ILD  920  in subsequent etching processes. The dielectric layer may be formed of a suitable material, such as silicon nitride, silicon carbonitride, or the like, using a suitable method such as CVD, PECVD, or FCVD. After the dielectric layer is formed, a planarization process, such as a CMP process, may be performed to achieve a level upper surface for the dielectric layer. After the planarization process, the upper surface of the dielectric layer (if any) or the upper surface of the ILD  920  is level with the upper surface of the dummy gate structures  802  to  812 , in some embodiments. 
     In some embodiments, some of the source/drain structures formed in the area  704 A may each function as one of the electrodes of a first type of interlayer decoupling capacitor. A portion of the ILD  920  disposed over such a source/drain structure can function as a portion of a dielectric medium of this type of interlayer decoupling capacitor. Details of such interlayer decoupling capacitors will be discussed below. 
     Referring to  FIGS. 6 and 10 , the method  600  proceeds to operation  608  in which a number of active (e.g., metal) gate structures  1002 ,  1004 ,  1006 ,  1008 ,  1010 , and  1012  are formed, in accordance with some embodiments. The cross-sectional view of semiconductor device  700  shown in  FIG. 10  may be cut along a lengthwise direction of the active region  704  (e.g., the X axis indicated in  FIG. 2A ). 
     The active gate structures  1002  to  1012  may be formed by replacing the dummy gate structures  802  to  812 , respectively. The active gate structures  1002  to  1012  can each include a gate dielectric layer, a metal gate layer, and one or more other layers that are not shown for clarity. For example, each of the active gate structures  1002  to  1012  may further include a capping layer and a glue layer. The capping layer can protect the underlying work function layer from being oxidized. In some embodiments, the capping layer may be a silicon-containing layer, such as a layer of silicon, a layer of silicon oxide, or a layer of silicon nitride. The glue layer can function as an adhesion layer between the underlying layer and a subsequently formed gate electrode material (e.g., tungsten) over the glue layer. The glue layer may be formed of a suitable material, such as titanium nitride. 
     The gate dielectric layer can include silicon oxide, silicon nitride, or multilayers thereof. In example embodiments, the gate dielectric layer can include a high-k dielectric material, and in these embodiments, the gate dielectric layer may have a k value greater than about  7 . 0 , and may include a metal oxide or a silicate of Hf, Al, Zr, La, Mg, Ba, Ti, Pb, or combinations thereof. The formation methods of the gate dielectric layer may include molecular beam deposition (MBD), atomic layer deposition (ALD), PECVD, and the like. A thickness of each of the gate dielectric layer may be between about 8 angstroms (Å) and about 20 Å, as an example. 
     The metal gate layer can include a P-type work function layer, an N-type work function layer, multi-layers thereof, or combinations thereof, in some embodiments. Accordingly, the metal gate layer may be referred to as a work function layer, in some embodiments. In the discussion herein, a work function layer may also be referred to as a work function metal. Example P-type work function metals that may be included in the gate structures for P-type devices include TiN, TaN, Ru, Mo, Al, WN, ZrSi 2 , MoSi 2 , TaSi 2 , NiSi 2 , WN, other suitable P-type work function materials, or combinations thereof. Example N-type work function metals that may be included in the gate structures for N-type devices include Ti, Ag, TaAl, TaA 1 C, TiAlN, TaC, TaCN, TaSiN, Mn, Zr, other suitable N-type work function materials, or combinations thereof. 
     A work function value is associated with the material composition of the work function layer, and thus, the material of the work function layer is chosen to tune its work function value so that a target threshold voltage Vt is achieved in the device that is to be formed. The work function layer(s) may be deposited by CVD, physical vapor deposition (PVD), ALD, and/or other suitable process. The thickness of a P-type work function layer may be between about 8 Å and about 15 Å, and the thickness of an N-type work function layer may be between about 15 Å and about 30 Å, as an example. 
     In some embodiments, some of the active gate structures formed in the area  704 A may each function as one of the electrodes of a second type of interlayer decoupling capacitor. A portion of another ILD disposed over such an active gate structure (which will be discussed below) can function as a dielectric medium of this type of interlayer decoupling capacitor. Details of such interlayer decoupling capacitors will be discussed below. 
     Referring to  FIGS. 6 and 11 , the method  600  proceeds to operation  610  in which a number of MEOL interconnect structures  1102 ,  1104 ,  1106 ,  1108 ,  1110 ,  1112 ,  1114 , and  1116  are formed, in accordance with some embodiments. The cross-sectional view of semiconductor device  700  shown in  FIG. 11  may be cut along a lengthwise direction of the active region  704  (e.g., the X axis indicated in  FIG. 2A ). 
     The interconnect structures  1102 - 1116 , formed of one or more metal materials (e.g., tungsten (W), copper (Cu), gold (Au), cobalt (Co), Ruthenium (Ru), or combinations thereof), is formed to electrically couple to one or more of the FEOL features (e.g., metal gate structures, source/drain structures). For example, the interconnect structures  1102 ,  1104 ,  1106 , and  1108  can electrically couple to the source/drain structures  902 ,  904 ,  908 , and  1108 , respectively, which are sometimes referred to as MD&#39;s  1102 ,  1104 ,  1106 , and  1108 . Each of the MD&#39;s  1102  to  1108  can extend through the ILD  920  to be in contact with the corresponding source/drain structure. Although not shown in the cross-sectional view of  FIG. 11 , it should be appreciated that the MD&#39;s  1102  to  1108  generally extend along a direction parallel to the gate structures (e.g., along the Y axis). In another example, the interconnect structures  1110 ,  1112 , and  1116 , formed as via structures, can electrically couple to the MD&#39;s  1102 ,  1106 , and  1108 , respectively, which are sometimes referred to as VD&#39;s  1102 ,  1112 , and  1116 . In yet another example, the interconnect structure  1114 , formed as a via structure, can electrically couple to the metal gate structure  1008 , which is sometimes referred to as VG  1114 . In some embodiments, each of the VD&#39;s  1102 ,  1112 , and  1116  and VG  1114  can extend through an ILD  1120  (disposed above the ILD  920 ) to be in contact with the corresponding MD or metal gate structure. 
     In some embodiments, some of the MD&#39;s formed in the area  704 A may each function as one of the electrodes of a third type of interlayer decoupling capacitor. A portion of the ILD  1120  disposed over such an MD can function as a dielectric medium of this type of interlayer decoupling capacitor. Details of such interlayer decoupling capacitors will be discussed below. 
     Referring to  FIGS. 6 and 12 , the method  600  proceeds to operation  612  in which a number of BEOL interconnect structures  1202 ,  1204 , and  1206  are formed, in accordance with some embodiments. The cross-sectional view of semiconductor device  700  shown in  FIG. 12  may be cut along a lengthwise direction of the active region  704  (e.g., the X axis indicated in  FIG. 2A ). 
     The interconnect structures  1202  to  1206 , formed of one or more metal materials (e.g., tungsten (W), copper (Cu), gold (Au), cobalt (Co), Ruthenium (Ru), or combinations thereof), is formed to electrically couple to one or more of the FEOL features (e.g., metal gate structures, source/drain structures) through the above-described MEOL interconnect structures. The interconnect structures  1202  to  1206  generally extend along a direction perpendicular to a lengthwise direction of the gate structures (e.g., along the X axis). The interconnect structures  1202  to  1206  are formed in the bottommost one of a number of BEOL layers (e.g., the next upper layer over the ILD  1120 ), which are sometimes referred to as M 0 &#39;s  1202 ,  1204 , and  1206 . 
     According to various embodiments, a first interlayer decoupling capacitor  1220  that have the source/drain structure  904 , the ILD  920  and ILD  1120 , and the M 0   1202  as its first electrode, dielectric medium, and second electrode, respectively, can be formed; a second interlayer decoupling capacitor  1230  that have the MD  1104 , the ILD  1120 , and the M 0   1202  as its second electrode, dielectric medium, and second electrode, respectively, can be formed; and a third interlayer decoupling capacitor  1240  that have the metal gate structure  1004 , the ILD  1120  and ILD  1120 , and the M 0   1204  as its first electrode, dielectric medium, and second electrode, respectively, can be formed. Further, to minimize their leakage current, one of the electrodes of each of these interlayer decoupling capacitors is electrically tied to either VDD or VSS. For example, the source/drain structure  904  of the interlayer decoupling capacitor  1220  is electrically tied to either VDD or VSS; the MD  1104  of the interlayer decoupling capacitor  1230  is electrically tied to either VDD or VSS; and the gate structure  1004  of the interlayer decoupling capacitor  1240  is electrically tied to either VDD or VSS. 
     In one aspect of the present disclosure, a semiconductor is disclosed. The semiconductor device includes a substrate. The semiconductor device includes an active region disposed over the substrate. The active region extends along a first lateral direction. The semiconductor device includes a plurality of first conductive structures operatively coupled to the active region. The plurality of first conductive structures extend along a second lateral direction perpendicular to the first lateral direction. The semiconductor device includes a plurality of second conductive structures disposed above the plurality of first conductive structures. The plurality of second conductive structures extend along the first lateral direction. The semiconductor device includes a first capacitor having a first electrode and a second electrode. The first electrode includes one of the plurality of first conductive structures and the active region, and the second electrode includes a first one of the plurality of second conductive structures. Each of the active region and the plurality of first conductive structures is electrically coupled to a power rail structure configured to carry a supply voltage. 
     In another aspect of the present disclosure, a semiconductor device is disclosed. The semiconductor device includes a first semiconductor channel extending along a first lateral direction. The semiconductor device includes a first epitaxial semiconductor structure coupled to an end of the first semiconductor channel. The semiconductor device includes a first interconnect structure electrically coupled to the first epitaxial semiconductor structure. The first interconnect structure extends along a second lateral direction perpendicular to the first lateral direction. The semiconductor device includes second interconnect structure vertically disposed above the first interconnect structure. The second interconnect structure extends along the first lateral direction. The semiconductor device includes a first decoupling capacitor having a first electrode and a second electrode. The first and second electrodes are formed by the first interconnect structure and the second interconnect structure, respectively. Each of the first epitaxial semiconductor structure and the first interconnect structure is electrically fixed at a supply voltage. 
     In yet another aspect of the present disclosure, a method for fabricating decoupling capacitors is disclosed. The method includes forming an active region over a substrate, wherein the active region extends along a first lateral direction. The method includes forming a plurality of first metal structures extending along a second lateral direction over the active region. The first metal structures are operatively coupled to respective portions of the active region. The method includes forming a plurality of second metal structures extending along the first lateral direction over the first metal structures. The second metal structures are separated from the first metal structures with at least one dielectric layer. The method includes forming a plurality of interlayer decoupling capacitors between the second metal structures and the first metal structures and/or between the second metal structures and the active region based on coupling the active region and the plurality of first metal structures to a structure that carries a supply voltage. 
     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.