Patent Publication Number: US-10763863-B2

Title: Semiconductor device for logic and memory co-optimization

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application No. 62/738,970, filed Sep. 28, 2018, the entirety of which is incorporated by reference herein. 
    
    
     BACKGROUND 
     The electronics industry has experienced an ever-increasing demand for smaller and faster electronic devices which are simultaneously able to support a greater number of increasingly complex and sophisticated functions. Accordingly, there is a continuing trend in the semiconductor industry to manufacture low-cost, high-performance, and low-power integrated circuits (ICs). Thus far these goals have been achieved in large part by scaling down semiconductor IC dimensions (e.g., minimum feature size) and thereby improving production efficiency and lowering associated costs. However, such scaling has also introduced increased complexity to the semiconductor manufacturing process. Thus, the realization of continued advances in semiconductor ICs and devices calls for similar advances in semiconductor manufacturing processes and technology. 
     Recently, multi-gate devices have been introduced in an effort to improve gate control by increasing gate-channel coupling, reduce OFF-state current, and reduce short-channel effects (SCEs). One such multi-gate device that has been introduced is the fin field-effect transistor (FinFET). FinFETs have been used in a variety of applications, for example, to implement logic devices/circuits and to provide static random-access memory (SRAM) devices, among others. Generally, logic devices are focused on performance (e.g., high Ion/Ioff ratio, low parasitic capacitance, etc.), while SRAM devices may focus on optimizing cell size and improving cell operation voltage, among other requirements. However, optimization of both logic and SRAM performance and/or design requirements has been challenging. As merely one example, reduction of a FinFET fin critical dimension (CD) may improve logic device Ion/Ioff performance but may also degrade SRAM latch-up performance. Thus, existing techniques have not proved entirely satisfactory in all respects. 
    
    
     
       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  is perspective view of an embodiment of a FinFET device according to one or more aspects of the present disclosure; 
         FIG. 2 , provides an exemplary circuit diagram of an SRAM cell, which can be implemented in a memory cell of a SRAM array, according to various aspects of the present disclosure; 
         FIG. 3  provides an exemplary plan view of a logic device, in accordance with some embodiments; 
         FIG. 4  provides a cross-sectional view of the logic device of  FIG. 3 , along a plane substantially parallel to a plane defined by section CC′ of  FIG. 3 , according to some embodiments; 
         FIG. 5  provides an exemplary plan view of an SRAM cell, in accordance with some embodiments; 
         FIG. 6  provides a cross-sectional view of the SRAM cell of  FIG. 5 , along a plane substantially parallel to a plane defined by section DD′ of  FIG. 5 , according to some embodiments; 
         FIG. 7  provides an exemplary plan view of another logic device, in accordance with some embodiments; 
         FIG. 8  provides a cross-sectional view of the logic device of  FIG. 7 , along a plane substantially parallel to a plane defined by section EE′ of  FIG. 7 , according to some embodiments; and 
         FIG. 9  is an exemplary method  900  of fabricating a semiconductor device, in accordance with one or more 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. Still further, when a number or a range of numbers is described with “about,” “approximate,” and the like, the term is intended to encompass numbers that are within a reasonable range including the number described, such as within +/−10% of the number described or other values as understood by person skilled in the art. For example, the term “about 5 nm” encompasses the dimension range from 4.5 nm to 5.5 nm. 
     It is also noted that the present disclosure presents embodiments in the form of multi-gate transistors or fin-type multi-gate transistors referred to herein as FinFET devices. Such a device may include a P-type metal-oxide-semiconductor FinFET device or an N-type metal-oxide-semiconductor FinFET device. The FinFET device may be a dual-gate device, tri-gate device, bulk device, silicon-on-insulator (SOI) device, and/or other configuration. One of ordinary skill may recognize other embodiments of semiconductor devices that may benefit from aspects of the present disclosure. For example, some embodiments as described herein may also be applied to gate-all-around (GAA) devices, Omega-gate (Ω-gate) devices, or Pi-gate (Π-gate) devices. 
     The present disclosure is generally related to semiconductor devices and methods of forming the same. In particular, embodiments of the present disclosure provide a process and/or structure for logic circuit and SRAM cell co-optimization to simultaneously achieve both high speed and low power consumption. 
     FinFETs have become a popular candidate for high performance and low leakage applications (e.g., such as for logic devices and/or circuits). In various examples, FinFET transistors employ a narrow fin width for short channel control, Ion/Ioff ratio improvement, and continuous scaling of the gate length. However, this narrow fin width has resulted in smaller top source/drain regions and has thus impacted the contact-to-source/drain landing margin and increased contact resistance. To address this issue, a longer contact layout was proposed, but gate-to-contact capacitance remained a major concern. FinFET devices having multiple fins have been used for high speed applications, but such devices suffered from increased leakage and power consumption. In some embodiments, a single fin FinFET device may be used to mitigate the leakage and power consumption issues, but this may also result in a loss of device speed. 
     For SRAM cells, where cell size optimization and cell operation voltage are key, the isolation rules between N+ and N-well (NW) regions, and between P+ and P-well (PW) regions have usually been pushed (reduced) to achieve a smaller SRAM cell size. However, the narrow fin width (e.g., required by logic devices) also negatively impacts N-well/P-well doping efficiency due to a thermal/implant out-diffusion effect, resulting in lightly-doped well regions. In some cases, the lightly doped well regions will result in worse leakage for N+/PW/NW structures and for P+/NW/PW structures. In various examples, thinner and more lightly doped fin well regions also detrimentally impact the well resistance and degrade the SRAM cell latch-up performance. Thus, existing techniques have not proved entirely satisfactory in all respects. 
     Embodiments of the present disclosure offer advantages over the existing art, though it is understood that other embodiments may offer different advantages, not all advantages are necessarily discussed herein, and no particular advantage is required for all embodiments. For example, embodiments discussed herein include structures and methods for the co-optimization of core (logic) devices and SRAM devices. In various embodiments, a semiconductor device may include individual device structures to meet both logic device requirements and SRAM requirements. In some cases, logic transistors may have a narrow fin CD for Ion/Ioff ratio improvement, and SRAM devices may have a thicker fin CD (e.g., compared to the logic devices) to avoid latch-up (e.g., by providing improved well resistance and N+PW/NW, P+/NW/PW isolation leakage improvement). In some examples, logic transistors may have a shorter gate electrode end-cap for contact-to-gate capacitance reduction, and SRAM devices may have a longer gate electrode end-cap for Vt stability improvement and Vcc_min reduction. In some embodiments, logic transistors may have wider well isolation space rules (e.g., N+ OD to N_Well, P+OD to P_well) for latch-up and well isolation leakage improvement, and SRAM devices may push (reduce) narrow well isolation space rules (e.g., N+ OD to N_Well, P+OD to P_Well) for cell size reduction. Generally, the various embodiments disclosed herein provide for the simultaneous optimization of logic device performance, SRAM cell scaling, and manufacturing process margin. Additional embodiments and advantages are discussed below and/or will be evident to those skilled in the art in possession of this disclosure. 
     Because one or more of the embodiments described herein are exemplified using FinFETs, for example for logic devices and for SRAM devices, a description of such devices is provided below with respect to  FIGS. 1 and 2 . However, it should be understood that other types of devices may benefit from one or more of the embodiments described herein. 
     Referring first to  FIG. 1 , illustrated therein is an exemplary FinFET device  100 . The FinFET device  100  includes one or more fin-based, multi-gate field-effect transistors (FETs). The FinFET device  100  includes a substrate  102 , at least one fin element  104  extending from the substrate  102 , isolation regions  106 , and a gate structure  108  disposed on and around the fin-element  104 . The substrate  102  may be a semiconductor substrate such as a silicon substrate. The substrate may include various layers, including conductive or insulating layers formed on a semiconductor substrate. The substrate may include various doping configurations depending on design requirements as is known in the art. The substrate may also include other semiconductors such as germanium, silicon carbide (SiC), silicon germanium (SiGe), or diamond. Alternatively, the substrate may include a compound semiconductor and/or an alloy semiconductor. Further, in some embodiments, the substrate may include an epitaxial layer (epi-layer), the substrate may be strained for performance enhancement, the substrate may include an SOI structure, and/or the substrate may have other suitable enhancement features. 
     The fin-element  104 , like the substrate  102 , may comprise silicon or another elementary semiconductor, such as germanium; a compound semiconductor including silicon carbide, gallium arsenide, gallium phosphide, indium phosphide, indium arsenide, and/or indium antimonide; an alloy semiconductor including SiGe, GaAsP, AlInAs, AlGaAs, InGaAs, GaInP, and/or GaInAsP; or combinations thereof. The fin elements  104  may be fabricated using suitable processes including photolithography and etch processes. The photolithography process may include forming a photoresist layer (resist) overlying the substrate (e.g., on a silicon layer), exposing the resist to a pattern, performing post-exposure bake processes, and developing the resist to form a masking element including the resist. In some embodiments, patterning the resist to form the making element may be performed using an electron beam (e-beam) lithography process. The masking element may then be used to protect regions of the substrate while an etch process forms recesses into the silicon layer, thereby leaving an extending fin element  104 . The recesses may be etched using a dry etch, a wet etch, and/or other suitable processes. Numerous other embodiments of methods to form the fin elements  104  on the substrate  102  may also be used. 
     Each of the plurality of fin elements  104  also include a source region  105  and a drain region  107  where the source/drain regions  105 ,  107  are formed in, on, and/or surrounding the fin element  104 . The source/drain regions  105 ,  107  may be epitaxially grown over the fin elements  104 . A channel region of a transistor is disposed within the fin element  104 , underlying the gate structure  108 , along a plane substantially parallel to a plane defined by section AA′ of  FIG. 1 . In some examples, the channel region of the fin includes a high-mobility material such as germanium, as well as any of the compound semiconductors or alloy semiconductors discussed above and/or combinations thereof. High-mobility materials include those materials with an electron mobility greater than silicon. For example, higher than Si which has an intrinsic electron mobility at room temperature (300 K) of around 1350 cm 2 /V-s and a hole mobility of around 480 cm 2 /V-s, in some instances. 
     The isolation regions  106  may be shallow trench isolation (STI) features. Alternatively, a field oxide, a LOCOS feature, and/or other suitable isolation features may be implemented on and/or within the substrate  102 . The isolation regions  106  may be composed of silicon oxide, silicon nitride, silicon oxynitride, fluorine-doped silicate glass (FSG), a low-k dielectric, combinations thereof, and/or other suitable material known in the art. In an embodiment, the isolation structures are STI features and are formed by etching trenches in the substrate  102 . The trenches may then be filled with isolating material, followed by a chemical mechanical polishing (CMP) process. However, other embodiments are possible. In some embodiments, the isolation regions  106  may include a multi-layer structure, for example, having one or more liner layers. 
     The gate structure  108  includes a gate stack including a gate dielectric layer  110 , and a metal layer  112  formed over the gate dielectric layer. In some embodiments, the gate dielectric layer  110  may include an interfacial layer formed over the channel region of the fin element  104  and a high-K dielectric layer over the interfacial layer. The interfacial layer of the gate dielectric layer  110  may include a dielectric material such as silicon oxide layer (SiO 2 ) or silicon oxynitride (SiON). The high-K dielectric layer of the gate dielectric layer  110  may include HfO 2 , TiO 2 , HfZrO, Ta 2 O 3 , HfSiO 4 , ZrO 2 , ZrSiO 2 , combinations thereof, or other suitable materials. In still other embodiments, the gate dielectric layer  110  may include silicon dioxide or another suitable dielectric. The gate dielectric layer  110  may be formed by chemical oxidation, thermal oxidation, atomic layer deposition (ALD), physical vapor deposition (PVD), chemical vapor deposition (CVD), and/or other suitable methods. 
     The metal layer  112  may include a conductive layer such as W, TiN, TaN, WN, Re, Ir, Ru, Mo, Al, Cu, Co, Ni, combinations thereof, and/or other suitable compositions. In some embodiments, the metal layer  112  may include a first group of metal materials for N-type FinFETs and a second group of metal materials for P-type FinFETs. Thus, the FinFET device  100  may include a dual work-function metal gate configuration. For example, the first metal material (e.g., for N-type devices) may include metals having a work function substantially aligned with a work function of the substrate conduction band, or at least substantially aligned with a work function of the conduction band of the channel region of the fin element  104 . Similarly, for example, the second metal material (e.g., for P-type devices) may include metals having a work function substantially aligned with a work function of the substrate valence band, or at least substantially aligned with a work function of the valence band of the channel region of the fin element  104 . Thus, the metal layer  112  may provide a gate electrode for the FinFET device  100 , including both N-type and P-type FinFET devices  100 . In some embodiments, the metal layer  112  may alternately include a polysilicon layer. The metal layer  112  may be formed using PVD, CVD, electron beam (e-beam) evaporation, and/or other suitable process. In some embodiments, sidewall spacers are formed on sidewalls of the gate structure  108 . The sidewall spacers may include a dielectric material such as silicon oxide, silicon nitride, silicon carbide, silicon oxynitride, or combinations thereof. 
     Referring now to  FIG. 2 , illustrated therein is an exemplary circuit diagram of an SRAM cell  200 , which can be implemented in a memory cell of a SRAM array, according to various aspects of the present disclosure. While  FIG. 2  illustrates a single-port SRAM cell, it will be understood that the various disclosed embodiments may be equally implemented in a multi-port SRAM cell (e.g., such as a dual-port SRAM cell), without departing from the scope of the present disclosure.  FIG. 2  has been simplified for the sake of clarity to better understand the inventive concepts of the present disclosure. Additional features can be added in the SRAM cell  200 , and some of the features described below can be replaced, modified, or eliminated in other embodiments of SRAM cell  200 . 
     The SRAM cell  200  includes six transistors: a pass-gate transistor PG- 1 , a pass-gate transistor PG- 2 , a pull-up transistor PU- 1 , a pull-up transistor PU- 2 , a pull-down transistor PD- 1 , and a pull-down transistor PD- 2 . Thus, in some examples, the SRAM cell  200  may be referred to as a  6 T SRAM cell. In operation, pass-gate transistor PG- 1  and pass-gate transistor PG- 2  provide access to a storage portion of the SRAM cell  200 , which includes a cross-coupled pair of inverters, an inverter  210  and an inverter  220 . Inverter  210  includes the pull-up transistor PU- 1  and the pull-down transistor PD- 1 , and inverter  220  includes the pull-up transistor PU- 2  and the pull-down transistor PD- 2 . In some implementations, pull-up transistors PU- 1 , PU- 2  are configured as P-type FinFETs, and pull-down transistors PD- 1 , PD- 2  are configured as N-type FinFETs. For example, pull-up transistors PU- 1 , PU- 2  each include a gate structure disposed over a channel region of an N-type fin structure (including one or more N-type fins), such that the gate structure interposes P-type source/drain regions of the N-type fin structure (e.g., P-type epitaxial source/drain features), where the gate structure and the N-type fin structure are disposed over an N-type well region; and pull-down transistors PD- 1 , PD- 2  each include a gate structure disposed over a channel region of a P-type fin structure (including one or more P-type fins), such that the gate structure interposes N-type source/drain regions of the P-type fin structure (e.g., N-type epitaxial source/drain features), where the gate structure and the P-type fin structure are disposed over a P-type well region. In some implementations, pass-gate transistors PG- 1 , PG- 2  are also configured as N-type FinFETs. For example, pass-gate transistors PG- 1 , PG- 2  each include a gate structure disposed over a channel region of a P-type fin structure (including one or more P-type fins), such that the gate structure interposes N-type source/drain regions of the P-type fin structure (e.g., N-type epitaxial source/drain features), where the gate structure and the P-type fin structure are disposed over a P-type well region. 
     A gate of pull-up transistor PU- 1  interposes a source (electrically coupled with a power supply voltage (Vdd)) and a first common drain (CD 1 ), and a gate of pull-down transistor PD- 1  interposes a source (electrically coupled with a power supply voltage (Vss)) and the first common drain. A gate of pull-up transistor PU- 2  interposes a source (electrically coupled with power supply voltage (Vdd)) and a second common drain (CD 2 ), and a gate of pull-down transistor PD- 2  interposes a source (electrically coupled with power supply voltage (Vss)) and the second common drain. In some implementations, the first common drain (CD 1 ) is a storage node (SN) that stores data in true form, and the second common drain (CD 2 ) is a storage node (SNB) that stores data in complementary form. The gate of pull-up transistor PU- 1  and the gate of pull-down transistor PD- 1  are coupled with the second common drain, and the gate of pull-up transistor PU- 2  and the gate of pull-down transistor PD- 2  are coupled with the first common drain. A gate of pass-gate transistor PG- 1  interposes a source (electrically coupled with a bit line BL) and a drain, which is electrically coupled with the first common drain. A gate of pass-gate transistor PG- 2  interposes a source (electrically coupled with a complementary bit line BLB) and a drain, which is electrically coupled with the second common drain. The gates of pass-gate transistors PG- 1 , PG- 2  are electrically coupled with a word line WL. In some implementations, pass-gate transistors PG- 1 , PG- 2  provide access to storage nodes SN, SNB during read operations and/or write operations. For example, pass-gate transistors PG- 1 , PG- 2  couple storage nodes SN, SN-B respectively to bit lines BL, BLB in response to voltage applied to the gates of pass-gate transistors PG- 1 , PG- 2  by WLs. 
     In view of the above discussion with respect to  FIGS. 1 and 2 , various embodiments of the present disclosure are now described.  FIGS. 3 and 7  provide exemplary plan views of a logic device, in accordance with some embodiments.  FIG. 5  provides an exemplary plan view of an SRAM cell, in accordance with some embodiments. In some embodiments, the logic and SRAM devices shown and described may be fabricated on the same substrate, for example, as part of an integrated semiconductor device that provides co-optimization of both logic and SRAM devices.  FIG. 4  provides a cross-sectional view of the logic device of  FIG. 3 , along a plane substantially parallel to a plane defined by section CC′ of  FIG. 3 ;  FIG. 6  provides a cross-sectional view of the SRAM cell of  FIG. 5 , along a plane substantially parallel to a plane defined by section DD′ of  FIG. 5 ; and  FIG. 8  provides a cross-sectional view of the logic device of  FIG. 7 , along a plane substantially parallel to a plane defined by section EE′ of  FIG. 7 . It is understood that the various figures, and any accompanying descriptions given, are merely exemplary and are not intended to be limiting beyond what is specifically recited in the claims that follow. In addition, the various figures shown and described have been simplified for the sake of clarity to better understand the inventive concepts of the present disclosure, and various features may be added, replaced, modified, or eliminated, without departing from the scope of the present disclosure. 
     With reference now to  FIGS. 3-6 , and in some embodiments, a semiconductor device (e.g., on a given substrate) may include a plurality of logic devices  300  (e.g., within a logic portion of the semiconductor device) and a plurality of SRAM devices  400  (e.g., within a memory portion of the semiconductor device).  FIG. 3  illustrates an exemplary plan view of the logic device  300 , and  FIG. 4  provides a cross-sectional view of the logic device  300 , along a plane substantially parallel to a plane defined by section CC′ of  FIG. 3 . In some embodiments, the logic device  300  includes a complementary metal-oxide-semiconductor (CMOS) inverter unit cell  302 . As shown, the unit cell  302  has an X-pitch ‘X 1 ’ parallel to a gate routing direction (e.g., parallel to a gate  316 ) and a Y-pitch ‘Y 1 ’ parallel to a fin active region routing direction (e.g., parallel to fins  308 ,  314 ). In some embodiments, the X-pitch ‘X 1 ’ is greater than the Y-pitch ‘Y 1 ’. For instance, in some cases, the X-pitch ‘X 1 ’ is about 2 to 3 times greater than the Y-pitch ‘Y 1 ’. Generally, in various embodiments, the logic device  300  may include an inverter, an AND gate, a NAND gate, an OR gate, a NOR gate, a flip-flop, scan logic, or combinational logic. Such logic devices may, in some examples, be interconnected to form a circuit including a plurality of logic cells (e.g., such as the logic device  300 ). In some embodiments, the logic device  300  includes a plurality of CMOS devices. In some cases, the various CMOS devices (e.g., such as the CMOS inverter of the logic device  300 ) may be formed by a single fin N-type FinFET and a single fin P-type FinFET. 
     For instance, the logic device  300  includes a P-type FinFET  304  formed over an N-well region  306  and including a single fin  308 , and an N-type FinFET  310  formed over a P-well region  312  and including a single fin  314 . In some embodiments, the X-pitch ‘X 1 ’ is defined from a left edge of the N-well region  306  to a right edge of the P-well region  312 . By way of example, the fin  308  is spaced from the fin  314  by a spacing ‘S 1 ’. In various cases, the fins  308 ,  314  may be similar to the fin elements  104 , discussed above with reference to  FIG. 1 . Fin cut regions  322 ,  324  identify regions where the fins  308 ,  314  are cut, for example, to provide isolation to neighboring devices. In some embodiments, the Y-pitch ‘Y 1 ’ is defined between the fin cut regions  322 ,  324 . The logic device  300  also includes a gate  316  that spans perpendicularly across both the fin  308  of the P-type FinFET  304  and the fin  314  of the N-type FinFET  310 . In some embodiments, the gate  316  extends beyond (overhangs) the fins  308 ,  314  by an end-cap length ‘E 1 ’. In various examples, the gate  316  may be similar to the gate structure  108 , discussed above with reference to  FIG. 1 . Thus, the gate  316  may include a dielectric layer  316 A (e.g., including an interfacial layer and a high-K dielectric layer) formed over a channel region  318  of the fin  308  and over a channel region  320  of the fin  314 , and a metal layer  316 B formed over the dielectric layer  316 A. In some embodiments, the end-cap length ‘E 1 ’ is at least two times greater than a thickness ‘T 1 ’ of the metal layer  316 B. The logic device  300  may also include isolation regions  334 , which in some cases may be similar to the isolation regions  106 , discussed above with reference to  FIG. 1 . 
     In some embodiments, each of the P-type FinFET  304  and the N-type FinFET  310  include source/drain regions on portions of the fins  308 ,  314  adjacent to and on either side of the gate  316 , and thus adjacent to and on either side of the channel regions  318 ,  320 . In some examples, the source/drain regions of the P-type FinFET  304  and the N-type FinFET  310  may be similar to the source/drain regions  105 ,  107 , discussed above with reference to  FIG. 1 . In some examples, a plurality of contacts may be directly (physically) connected to the source/drain regions. For example, the P-type FinFET  304  may include a source contact  326  and a drain contact  328  connected to respective source/drain regions of the P-type FinFET  304 . Similarly, the N-type FinFET  310  may include a source contact  330  and a drain contact  332  connected to respective source/drain regions of the N-type FinFET  310 . In some embodiments, the X-pitch ‘X 1 ’ is defined from a left edge of the source contact  326  to a right edge of the source contact  330 . 
       FIG. 5  illustrates an exemplary plan view of the SRAM device  400 , and  FIG. 6  provides a cross-sectional view of the SRAM device  400 , along a plane substantially parallel to a plane defined by section DD′ of  FIG. 5 . In particular, the SRAM device  400  shows an SRAM unit cell  502  having an X-pitch ‘X 2 ’ parallel to a gate routing direction (e.g., parallel to gates  518 ,  520 ,  522 ,  524 ) and a Y-pitch ‘Y 2 ’ parallel to a fin active region routing direction (e.g., parallel to fins  510 ,  512 ,  514 ,  516 ). In some examples, the X-pitch ‘X 2 ’ is greater than the Y-pitch ‘Y 2 ’. For instance, in some cases, the X-pitch ‘X 2 ’ is about 2 to 3 times greater than the Y-pitch ‘Y 2 ’. In some embodiments, the SRAM device  400  may include a plurality of SRAM unit cells  502  arranged, for example, in a plurality of columns and rows (e.g., to provide a memory array). In some cases, the SRAM unit cell  502  may include an N-well region  504  disposed between two P-well regions  506 ,  508 . In some embodiments, the X-pitch ‘X 2 ’ is defined from a left edge of the P-well region  506  to a right edge of the P-well region  508 . In some embodiments, the P-well region  506  includes an N-type FinFET pass gate (PG- 1 ) transistor and an N-type FinFET pull-down (PD- 1 ) transistor, and the P-well region  508  includes an N-type FinFET pass gate (PG- 2 ) transistor and an N-type FinFET pull-down (PD- 2 ) transistor. In some examples, the N-well region  504  may include a first P-type FinFET pull-up (PU- 1 ) and a second P-type FinFET pull-up (PU- 2 ) transistor. 
     In various embodiments, the PG- 1 , PG- 2 , PD- 1 , PD- 2 , PU- 1 , and PU- 2  transistors are formed using a single fin FinFET. For example, the PG- 1 , PG- 2 , PD- 1 , and PD- 2  transistors may be formed by a single fin N-type FinFET, and the PU- 1  and PU- 2  transistors may be formed by a single fin P-type FinFET. As shown in the example of  FIG. 5 , the PG- 1  and PD- 1  transistors include a single fin  510 , the PG- 2  and PD- 2  transistors include a single fin  512 , and the PU- 1  and PU- 2  transistors include single fins  514  and  516 , respectively. In various examples, a fin spacing ‘S 2 ’ may be defined (e.g., such as between the fin  510  and the fin  514 , or between other pairs of fins). The fins  510 ,  512 ,  514 , and  516  may be similar to the fin elements  104 , discussed above with reference to  FIG. 1 . 
     Each of the PG- 1 , PG- 2 , PD- 1 , PD- 2 , PU- 1 , and PU- 2  transistors of the SRAM device  400  also include a gate, as shown in the example of  FIG. 5 . For instance, PG- 1  includes a gate  518  that spans perpendicularly across a channel region  534  of the fin  510 , PG- 2  includes a gate  520  that spans perpendicularly across a channel region  526  of the fin  512 , PD- 1  and PU- 1  include a gate  522  that spans perpendicularly across a channel region  528  of the fin  510  and across a channel region  530  of the fin  514 , and PD- 2  and PU- 2  include a gate  524  that spans perpendicularly across a channel region  536  of the fin  512  and across a channel region  538  of the fin  516 . In some embodiments, a gate may extend beyond (overhang) a fin by an end-cap length ‘E 2 ’ (e.g., such as the gate  522  extending beyond the fin  510 , or another gate extending beyond a respective fin over which it is disposed). In various examples, the gates  518 ,  520 ,  522 , and  524  may be similar to the gate structure  108 , discussed above with reference to  FIG. 1 . Thus, the gates  518 ,  520 ,  522 ,  524  may include a dielectric layer (e.g., including an interfacial layer and a high-K dielectric layer) formed over respective channel regions of the fins over which the various gates are disposed, and a metal layer formed over the dielectric layer. As one example, and as shown in  FIGS. 5 and 6 , the gate  520  of PG- 2  may include a dielectric layer  520 A formed over the channel region  526  of the fin  512  and a metal layer  520 B formed over the dielectric layer  520 A, and the gate  522  of PD- 1  and PU- 1  may include a dielectric layer  522 A formed over the channel region  528  of the fin  510  and over a channel region  530  of the fin  514 , and a metal layer  522 B formed over the dielectric layer  522 A. In some embodiments, the end-cap length ‘E 2 ’ is at least two times greater than a thickness ‘T 2 ’ of the metal layer  522 B. The SRAM device  400  may also include isolation regions  532 , which in some cases may be similar to the isolation regions  106 , discussed above with reference to  FIG. 1 . 
     In various embodiments, each of the PG- 1 , PG- 2 , PD- 1 , PD- 2 , PU- 1 , and PU- 2  transistors of the SRAM device  400  includes source/drain regions on portions of their respective fins adjacent to and on either side of their respective gates, and thus adjacent to and on either side of their respective channel regions (e.g., such as the channel regions  526 ,  528 ,  530 ,  534 ,  536 , and  538 ). In some examples, the source/drain regions of each of the PG- 1 , PG- 2 , PD- 1 , PD- 2 , PU- 1 , and PU- 2  transistors may be similar to the source/drain regions  105 ,  107 , discussed above with reference to  FIG. 1 . In some examples, a plurality of contacts may be directly (physically) connected to the source/drain regions of the SRAM device  400 . For example, the PG- 1  transistor may include a source contact  540  (bit-line node ‘BL’) and a drain contact  542  (first common drain) connected to respective source/drain regions of the PG- 1  transistor, the PG- 2  transistor may include a source contact  544  (bit-line-bar node ‘BLB’) and a drain contact  546  (second common drain) connected to respective source/drain regions of the PG- 2  transistor, the PD- 1  transistor may include a source contact  548  (CVss node) and the drain contact  542  (first common drain) connected to respective source/drain regions of the PD- 1  transistor, the PD- 2  transistor may include a source contact  550  (CVss node) and the drain contact  546  (second common drain) connected to respective source/drain regions of the PD- 2  transistor, the PU- 1  transistor may include a source contact  552  (CVdd node) and the drain contact  542  (first common drain) connected to respective source/drain regions of the PU- 1  transistor, and the PU- 2  transistor may include a source contact  554  (CVdd node) and the drain contact  546  (second common drain) connected to respective source/drain regions of the PU- 2  transistor. In some cases, the X-pitch ‘X 2 ’ is defined between the source contact  548  (CVss node) and the source contact  550  (CVss node). In some embodiments, the Y-pitch ‘Y 2 ’ is defined between the source contact  544  (BLB),  548  (CVss node), or  552  (CVdd node) and the source contact  540  (BL),  550  (CVss node), or  554  (CVdd node). 
     With respect to the logic device  300  of  FIGS. 3 and 4 , it is noted that the N-type FinFET  310  has a first fin width (W 1 ) in the channel region  320  of the fin  314 , and the P-type FinFET  304  has a second fin width (W 2 ) in the channel region  318  of the fin  308 . With respect to the SRAM device  400  of  FIGS. 5 and 6 , it is noted that the PD transistors (e.g., the PD- 1  and the PD- 2  transistors) have a third fin width (W 3 ), for example, in the channel region  528  of the fin  510  and/or in the channel region  536  of the fin  512 . Further, the PU transistors (e.g., the PU- 1  and the PU- 2  transistors) have a fourth fin width (W 4 ), for example, in the channel region  530  of the fin  514  and/or in the channel region  538  of the fin  516 . 
     In some cases, the first fin width (W 1 ) of the logic device  300  is narrower than the third fin width (W 3 ) of the SRAM device  400 . In some embodiments, the first fin width (W 1 ) of the logic device  300  is narrower than the third fin width (W 3 ) of the SRAM device  400  by at least 5%, and the second fin width (W 2 ) of the logic device  300  is narrower than fourth fin width (W 4 ) of the SRAM device  400  by at least by 5%. In some cases, the first fin width (W 1 ) of the logic device  300  is narrower than the third fin width (W 3 ) of the SRAM device  400  by at least 10%. By way of example, active region fin width ratios may also be defined, where for instance W 3 /W 1  is greater than 1.05, and where W 4 /W 2  is greater than 1.05. As noted, the N-type FinFET  310  of the logic device  300  has a first end-cap length ‘E 1 ’ and the PD transistors (e.g., the PD- 1  or the PD- 2  transistor) of the SRAM device  400  have a second end-cap length ‘E 2 ’. In some embodiments, the second end-cap length ‘E 2 ’ is longer than first end-cap length ‘E 1 ’ by at least 10%. In some embodiments, an end-cap length ratio may be defined, where for instance E 2 /E 1  is greater than 1.1. Additionally, as noted above, the CMOS structure of the logic device  300  (e.g., including the P-type FinFET  304  and the N-type FinFET  310 ) has a first active region space ‘S 1 ’ between the channel region  318  of the P-type FinFET  304  and the channel region  320  of the N-type FinFET  310  (e.g., between the fin  308  and the fin  314 ). Further, the CMOS structure of the SRAM device  400  (e.g., such as the N-type FinFET PD- 1  and the P-type FinFET PU- 1 ) has a second active region space ‘S 2 ’ between the PD-channel region and PU-channel region (e.g., such as between the channel region  528  of the N-type FinFET PD- 1  and the channel region  530  of the P-type FinFET PU- 1 ). In some embodiments, the first active region space ‘S 1 ’ is larger than second active region space ‘S 2 ’ by at least 20%. In addition, in some embodiments and with respect to the unit cell  302  X-pitch Y-pitch ‘Y 1 ’, and the SRAM unit cell  502  X-pitch ‘X 2 ’, Y-pitch ‘Y 2 ’, the X-pitch ‘X 1 ’ is substantially the same as the X-pitch ‘X 2 ’. In some embodiments, the Y-pitch ‘Y 1 ’ may be substantially the same as, or greater than, the Y-pitch ‘Y 2 ’. As such, in various examples, a ratio of the Y-pitches ‘Y 1 TY 2 ’ may be equal to 1, 1.5, 2, 2.5, or 3. Also, in some examples, the gate dielectric material and/or thickness (e.g., of the dielectric layer  316 A and/or the dielectric layer  522 A) of the logic device  300  and the SRAM device  400  is substantially the same. 
     Referring now to  FIGS. 7 and 8 ,  FIG. 7  illustrates an exemplary plan view of a logic device  700 , and  FIG. 8  provides a cross-sectional view of the logic device  700 , along a plane substantially parallel to a plane defined by section EE′ of  FIG. 7 . In some embodiments, the logic device  700  may be used instead of the logic device  300 . Thus, in some cases, a semiconductor device (e.g., on a given substrate) may include a plurality of logic devices  700  and a plurality of SRAM devices (e.g., such as the SRAM device  400 ). In various aspects, the logic device  700  is substantially the same as the logic device  300 , discussed above with reference to  FIGS. 3 and 4 . As such, one or more of the features described above with reference to the logic device  300  may also apply to the logic device  700 . Thus, for clarity of discussion, some features of the logic device  700  may be only discussed briefly below. 
     The logic device  700  may include a CMOS inverter unit cell  702  having the X-pitch ‘X 1 ’ parallel to a gate routing direction (e.g., parallel to a gate  716 ) and the Y-pitch ‘Y 1 ’ parallel to a fin active region routing direction (e.g., parallel to fins  708 ,  709 ,  714 ,  715 ). In some embodiments, the X-pitch ‘X 1 ’ is greater than the Y-pitch ‘Y 1 ’. For instance, in some cases, the X-pitch ‘X 1 ’ is about 2 to 3 times greater than the Y-pitch ‘Y 1 ’. While shown as including an inverter, the logic device  700  may include a variety of other logic gates, devices, or circuits, as noted above. In some embodiments, the logic device  700  includes a plurality of CMOS devices formed using a double fin N-type FinFET and a double fin P-type FinFET. 
     For example, the logic device  700  includes a P-type FinFET  704  formed over an N-well region  706  and including double fins (e.g., a fin  708  and a fin  709 ), and an N-type FinFET  710  formed over a P-well region  712  and including double fins (e.g., a fin  714  and a fin  715 ). In some embodiments, the X-pitch ‘X 1 ’ is defined from a left edge of the N-well region  706  to a right edge of the P-well region  712 . Fin cut regions  722 ,  724  identify regions where the fins are cut, for example, to provide isolation to neighboring devices. In some embodiments, the Y-pitch ‘Y 1 ’ is defined between the fin cut regions  722 ,  724 . The logic device  700  also includes a gate  716  that spans perpendicularly across the double fins of the P-type FinFET  704  and the double fins of the N-type FinFET  710 . The gate  716  may include a dielectric layer  716 A (e.g., including an interfacial layer and a high-K dielectric layer) formed over channel regions  718  of the double fins of the P-type FinFET  704  and over channel regions  720  of the double fins of the N-type FinFET  710 , and a metal layer  716 B formed over the dielectric layer  716 A. The logic device  700  may also include isolation regions  734 , in various embodiments. 
     In some cases, each of the P-type FinFET  704  and the N-type FinFET  710  include source/drain regions on portions of the double fins adjacent to and on either side of the gate  716 , and thus adjacent to and on either side of the channel regions  718 ,  720 . In some examples, a plurality of contacts may be directly (physically) connected to the source/drain regions. For example, the P-type FinFET  704  may include a source contact  726  and a drain contact  728  connected to respective source/drain regions of the P-type FinFET  704 . Similarly, the N-type FinFET  710  may include a source contact  730  and a drain contact  732  connected to respective source/drain regions of the N-type FinFET  710 . In some embodiments, the X-pitch ‘X 1 ’ is defined from a left edge of the source contact  726  to a right edge of the source contact  730 . 
     In various embodiments, and with respect to the logic device  700  of  FIGS. 7 and 8 , it is noted that the double fins of the N-type FinFET  710  (fins  714 ,  715 ) each have the first fin width (W 1 ) in the channel regions  720 , and the double fins of the P-type FinFET  704  (fins  708 ,  709 ) each have the second fin width (W 2 ) in the channel region  718 . As discussed above, and with respect to the SRAM device  400  of  FIGS. 5 and 6 , the PD transistors (e.g., the PD- 1  and the PD- 2  transistors) have a third fin width (W 3 ), and the PU transistors (e.g., the PU- 1  and the PU- 2  transistors) have a fourth fin width (W 4 ). 
     In some embodiments, first fin width (W 1 ) of the logic device  700  is narrower than the third fin width (W 3 ) of the SRAM device  400  by at least 5%, and the second fin width (W 2 ) of the logic device  700  is narrower than fourth fin width (W 4 ) of the SRAM device  400  by at least by 5%. In some cases, the first fin width (W 1 ) of the logic device  700  is narrower than the third fin width (W 3 ) of the SRAM device  400  by at least 10%. By way of example, the active region fin width ratios (e.g., for the logic device  700  and the SRAM device  400 ) may include W 3 /W 1  is greater than 1.05, and W 4 /W 2  is greater than 1.05. The N-type FinFET  310  of the logic device  700  has the first end-cap length ‘E 1 ’ and the PD transistors (e.g., the PD- 1  or the PD- 2  transistor) of the SRAM device  400  have the second end-cap length ‘E 2 ’. In some embodiments, the second end-cap length ‘E 2 ’ is longer than first end-cap length ‘E 1 ’ by at least 10%. In addition, the CMOS structure of the logic device  700  (e.g., including the P-type FinFET  704  and the N-type FinFET  710 ) has a first active region space ‘S 1 ’ between the channel regions  718  of the P-type FinFET  704  and the channel regions  720  of the N-type FinFET  710  (e.g., between the fin  709  and the fin  715 ). In various examples, the SRAM device  400  has a second active region space ‘S 2 ’ between the PD-channel region and PU-channel region, as described above. In some embodiments, the first active region space ‘S 1 ’ is larger than second active region space ‘S 2 ’ by at least 20%. With respect to the unit cell  702  X-pitch ‘X 1 ’, Y-pitch ‘Y 1 ’, and the SRAM unit cell  502  X-pitch ‘X 2 ’, Y-pitch ‘Y 2 ’, the X-pitch ‘X 1 ’ is substantially the same as the X-pitch ‘X 2 ’. In some embodiments, the Y-pitch ‘Y 1 ’ may be substantially the same as, or greater than, the Y-pitch ‘Y 2 ’. As such, in various examples, a ratio of the Y-pitches ‘Y 1 TY 2 ’ may be equal to 1, 1.5, 2, 2.5, or 3. Also, in some examples, the gate dielectric material and/or thickness (e.g., of the dielectric layer  716 A and/or the dielectric layer  522 A) of the logic device  700  and the SRAM device  400  is substantially the same. 
     As a further description of the above disclosure, the fin widths (W 1 -W 4 ) may be defined within a fin top portion, a fin middle portion, or a fin bottom portion. In addition, the structure of the gate (e.g., such as the gate  316 ,  518 ,  520 ,  522 ,  524 ,  716 ) may include multiple material structures selected from a group such as a poly-gate/SiON structure, a metal(s)/high-K dielectric structure, an Al/refractory metal(s)/high-K dielectric structure, a silicide/high-K dielectric structure, or a combination thereof. In some embodiments, the N-type FinFETs of the logic devices  300 ,  700  and of the SRAM device  400  may include N-type doped (e.g., phosphorus (P31 or other), As, or both) epitaxially grown source/drain regions. In some embodiments, the logic devices  300 ,  700  have a first source/drain epi width and the SRAM device  400  has a second epi width, where the second epi width is wider than first epi width by at least 5%. In some embodiments, the P-type FinFETs of the logic devices  300 ,  700  and of the SRAM device  400  may include P-type doped (e.g., boron, B11 or other) epitaxially grown source/drain regions. In some embodiments, the logic devices  300 ,  700  have a third S/D epi width and the SRAM device  400  has a fourth epi width, where the fourth epi width is wider than third epi width by at least 5%. In some embodiments, the material of the N-type doped source/drain region includes an epi profile, and the epi material may be selected from a group including SiP, SiC, SiPC, SiAs, Si, or a combination thereof. In some cases, the material of the P-type doped source/drain region includes an epi profile, and the epi material may be selected from a group including SiGe, SiGeC, Ge, or a combination thereof. In some embodiments, the contact layers (e.g., contacting the source/drain regions) may include multiple metal materials that may be selected from a group including Ti, TiN, TaN, Co, W, Al, Ru, Cu, or a combination thereof. In some embodiments, the substrate material of the disclosed devices may be selected from a group including bulk-Si, SiP, SiGe, SiC, SiPC, Ge, SOI-Si, SOI-SiGe, III-VI materials, a combination thereof, or other materials as described above. In some embodiments, the transistors disclosed herein may include FinFET structures selected from a group including a 2D-finFET structure, a 3D-finFET structure, or a combination thereof. 
     Referring now to  FIG. 9 , illustrated is an exemplary general method  900  of fabricating a semiconductor device (e.g., including one or more of the devices  100 ,  200 ,  300 ,  400 , or  700 ) in accordance with one or more embodiments. It is understood that parts of the method  900  and/or the semiconductor device fabricated thereby may be fabricated by a well-known CMOS technology process flow, and thus some processes are only briefly described herein. 
     The method  900  begins at block  902  where a substrate (e.g., such as a silicon substrate) is provided. In some examples, the substrate may include a variety of materials and/or configurations, as discussed above with respect to the substrate  102  of  FIG. 1 . The method  900  proceeds to block  904  where fin structures are formed. In some embodiments, formation of the fin structures includes deposition of a first group of dielectric layers (e.g., having a thickness of between about 100 A-2000 A) on the substrate. Dummy patterns may be formed, where for example, photolithography and etching steps may be used to partially remove the first group of dielectric layers, leaving behind a portion of the first group dielectric layers as well as the dummy patterns. In some embodiments, a second group of dielectric layers is then deposited (e.g., having a thickness of between about 20 A-700 A) and etched back to form at least two spacers on opposing sidewalls of the dummy patterns. In some cases, the dummy patterns are removed (e.g., by a wet etch, a dry etch, or combination thereof) such that the spacers remain. A lithography process may be performed to expose a first fin portion (e.g., a logic device fin portion or an SRAM device fin portion), and an extra etch process may be performed for spacer layer CD trim down. In some embodiments, the remaining spacer layers may be used as a hard mask to partially remove the Si substrate. In some cases, another lithography and etch process (e.g., cut layer process) may be performed to remove unnecessary fin region(s). After formation of the fin lines, the method  900  proceeds to block  906  where well and channel doping may be performed. Thereafter, the method  900  proceeds to block  908  where a gate structure is formed. By way of example, the gate structure may include one or more of the gate structures discussed above (e.g., including a gate dielectric layer and a metal layer over the gate dielectric layer). The method  900  then proceeds to block  910  where device source/drain regions are formed, such as the source/drain regions discussed above. The method  900  then proceeds to block  912  where and contacts, VIAs, and metal interconnect layers may be formed. In some embodiments, the method  900  may continue with further processing to form various features and regions known in the art. 
     Thus, the various embodiments described herein offer several advantages over the existing art. It will be understood that not all advantages have been necessarily discussed herein, no particular advantage is required for all embodiments, and other embodiments may offer different advantages. For example, embodiments discussed herein include structures and methods for the co-optimization of core (logic) devices and SRAM devices. In various embodiments, a semiconductor device may include individual device structures to meet both logic device requirements and SRAM requirements. In some cases, logic transistors may have a narrow fin CD for Ion/Ioff ratio improvement, and SRAM devices may have a thicker fin CD (e.g., compared to the logic devices) to avoid latch-up (e.g., by providing improved well resistance and N+PW/NW, P+/NW/PW isolation leakage improvement). In some examples, logic transistors may have a shorter gate electrode end-cap for contact-to-gate capacitance reduction, and SRAM devices may have a longer gate electrode end-cap for Vt stability improvement and Vcc_min reduction. In some embodiments, logic transistors may have wider well isolation space rules (e.g., N+ OD to N_Well, P+OD to P_well) for latch-up and well isolation leakage improvement, and SRAM devices may push (reduce) narrow well isolation space rules (e.g., N+ OD to N_Well, P+OD to P_Well) for cell size reduction. Generally, the various embodiments disclosed herein provide for the simultaneous optimization of logic device performance, SRAM cell scaling, and manufacturing process margin. Additional embodiments and advantages will be evident to those skilled in the art in possession of this disclosure. 
     Thus, one of the embodiments of the present disclosure described a semiconductor device including a logic portion and a memory portion. In some embodiments, a logic device is disposed within the logic portion. In some cases, the logic device includes a single fin N-type FinFET and a single fin P-type FinFET. In some examples, a static random-access memory (SRAM) device is disposed within the memory portion. The SRAM device includes an N-well region disposed between two P-well regions, where the two P-well regions include an N-type FinFET pass gate (PG) transistor and an N-type FinFET pull-down (PD) transistor, and where the N-well region includes a P-type FinFET pull-up (PU) transistor. 
     In another of the embodiments, discussed is a circuit including a first circuit region and a second circuit region. In some embodiments, a logic circuit is disposed within the first circuit region. In some cases, the logic circuit includes a double fin N-type FinFET and a double fin P-type FinFET. In various embodiments, a memory circuit is disposed within the second circuit region. In some examples, the memory circuit includes a first plurality of single fin N-type FinFETs and a second plurality of single fin P-type FinFETs. 
     In yet another of the embodiments, discussed is a semiconductor device including a plurality of logic portions and a plurality of memory portions disposed on a substrate. In some examples, a plurality of CMOS devices is disposed within the plurality of logic portions, where each CMOS device includes a single fin N-type FinFET having a first fin width (W 1 ) and a single fin P-type FinFET having a second fin width (W 2 ). In some embodiments, a plurality of static random-access memory (SRAM) devices is disposed within the plurality of memory portions, where the plurality of SRAM devices are arranged in a plurality of rows and columns. In some cases, each SRAM device includes an N-type FinFET pass gate (PG) transistor and an N-type FinFET pull-down (PD) transistor disposed within a P-well region and a P-type FinFET pull-up (PU) transistor disposed within an N-well region. In some embodiments, the N-type FinFET PD transistor has a third fin width (W 3 ) and the P-type FinFET PU transistor has a fourth fin width (W 4 ). In various examples, the first fin width (W 1 ) is narrower than the third fin width (W 3 ). 
     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.