Patent Publication Number: US-11653499-B2

Title: Semiconductor devices including staircase structures

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 16/202,999, filed Nov. 28, 2018, now U.S. Patent 10,910,395, issued Feb. 2, 2021 which is a divisional of U.S. patent application Ser. No. 15/058,921, filed Mar. 2, 2016, now U.S. Pat. No. 10,373,970, issued Aug. 6, 2019, the disclosure of each of which is hereby incorporated herein in its entirety by this reference. 
    
    
     TECHNICAL FIELD 
     The disclosure, in various embodiments, relates generally to the field of semiconductor device design and fabrication. More specifically, the disclosure relates to semiconductor device structures including staircase structures, and to related methods and electronic systems. 
     BACKGROUND 
     A continuing goal of the semiconductor industry has been to increase the memory density (e.g., the number of memory cells per memory die) of memory devices, such as non-volatile memory devices (e.g., NAND Flash memory devices). One way of increasing memory density in non-volatile memory devices is to utilize vertical memory array (also referred to as a “three-dimensional (3D) memory array”) architectures. A conventional vertical memory array includes semiconductor pillars extending through openings in tiers of conductive structures (e.g., word line plates, control gate plates) and dielectric materials at each junction of the semiconductor pillars and the conductive structures. Such a configuration permits a greater number of switching devices (e.g., transistors) to be located in a unit of die area by building the array upwards (e.g., longitudinally, vertically) on a die, as compared to structures with conventional planar (e.g., two-dimensional) arrangements of transistors. 
     Conventional vertical memory arrays include electrical connections between the conductive structures and access lines (e.g., word lines) so that memory cells in the vertical memory array can be uniquely selected for writing, reading, or erasing operations. One method of forming such an electrical connection includes forming a so-called “staircase” or “stair step” structure at edges of the tiers of conductive structures. The staircase structure includes individual “steps” defining contact regions of the conductive structures upon which contact structures can be positioned to provide electrical access to the conductive structures. Unfortunately, conventional staircase structure fabrication techniques can segment one or more conductive structures of a given tier, resulting in discontinuous conductive paths through the tier that can require the use of multiple (e.g., more than one) switching devices to drive voltages completely across the tier and/or in opposing directions across the tier. 
     There remains a need for new semiconductor device structures, such as memory array blocks for 3D non-volatile memory devices (e.g., 3D NAND Flash memory devices), as well as for associated memory devices and electronic systems including the semiconductor device structures, and simple, cost-efficient methods of forming semiconductor device structures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS.  1 A through  1 G  are perspective ( FIGS.  1 A through  1 F ) and top-down ( FIG.  1 G ) views illustrating a method of forming a semiconductor device structure, in accordance with embodiments of the disclosure. 
         FIG.  2    is a perspective view of a semiconductor device structure, in accordance with additional embodiments of the disclosure. 
         FIGS.  3 A through  3 F  are perspective ( FIGS.  3 A through  3 E ) and top-down ( FIG.  3 F ) views illustrating a method of forming a semiconductor device structure, in accordance with further embodiments of the disclosure. 
         FIG.  4    is a perspective view of a semiconductor device structure, in accordance with additional embodiments of the disclosure. 
         FIG.  5    is a perspective view of a semiconductor device structure, in accordance with further embodiments of the disclosure. 
         FIG.  6    is a schematic block diagram illustrating an electronic system in accordance with embodiments of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Semiconductor device structures (e.g., memory array blocks) including staircase structures are described, as are related methods and electronic systems. In some embodiments, a semiconductor device structure includes stacked tiers each including at least one conductive structure and at least one insulating structure longitudinally adjacent the at least one conductive structure, one or more staircase structures including steps defined by lateral ends of the stacked tiers, and one or more openings extending through the stacked tiers and continuously across an entire length of the at least one staircase structure. The conductive structure of each of the stacked tiers may extend continuously from at least one of the steps of the at least one staircase structure and around the opening (e.g., around ends and one or more sides of the opening) to form a continuous conductive path extending completely across each of the stacked tiers. In additional embodiments, a semiconductor device structure formed in accordance with the methods of the disclosure includes stacked tiers each including conductive structures and insulating structures longitudinally adjacent the conductive structures, stadium structures each including opposing staircase structures having steps defined by lateral ends of the stacked tiers, at least one opening laterally intervening between at least two of the stadium structures and extending through the stacked tiers and continuously across entire lengths of the at least two stadium structures, conductive contact structures coupled to the conductive structures of the stacked tiers at steps of the opposing staircase structures of at least one of the stadium structures, and conductive routing structures coupled to and extending completely between pairs of the conductive contact structures to form at least one continuous conductive path extending completely across each of the stacked tiers. The structures and methods of the disclosure may permit individual (e.g., single) switching devices (e.g., transistors) of at least one string driver device electrically connected to one or more conductive structures of an individual tier to drive voltages completely across and/or in opposing directions across the tier. The structures and methods of the disclosure may decrease the number of switching devices and interconnections required to effectively operate a memory device, and may increase one or more of memory device performance, scalability, efficiency, and simplicity as compared to many conventional structures and methods. 
     The following description provides specific details, such as material compositions and processing conditions, in order to provide a thorough description of embodiments of the present disclosure. However, a person of ordinary skill in the art would understand that the embodiments of the present disclosure may be practiced without employing these specific details. Indeed, the embodiments of the present disclosure may be practiced in conjunction with conventional semiconductor fabrication techniques employed in the industry. In addition, the description provided below does not form a complete process flow for manufacturing a semiconductor device (e.g., a memory device). The semiconductor device structures described below do not form a complete semiconductor device. Only those process acts and structures necessary to understand the embodiments of the present disclosure are described in detail below. Additional acts to form a complete semiconductor device from the semiconductor device structures may be performed by conventional fabrication techniques. 
     Drawings presented herein are for illustrative purposes only, and are not meant to be actual views of any particular material, component, structure, device, or system. Variations from the shapes depicted in the drawings as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments described herein are not to be construed as being limited to the particular shapes or regions as illustrated, but include deviations in shapes that result, for example, from manufacturing. For example, a region illustrated or described as box-shaped may have rough and/or nonlinear features, and a region illustrated or described as round may include some rough and/or linear features. Moreover, sharp angles that are illustrated may be rounded, and vice versa. Thus, the regions illustrated in the figures are schematic in nature, and their shapes are not intended to illustrate the precise shape of a region and do not limit the scope of the present claims. The drawings are not necessarily to scale. Additionally, elements common between figures may retain the same numerical designation. 
     As used herein, the terms “vertical”, “longitudinal”, “horizontal”, and “lateral” are in reference to a major plane of a structure and are not necessarily defined by earth&#39;s gravitational field. A “horizontal” or “lateral” direction is a direction that is substantially parallel to the major plane of the structure, while a “vertical” or “longitudinal” direction is a direction that is substantially perpendicular to the major plane of the structure. The major plane of the structure is defined by a surface of the structure having a relatively large area compared to other surfaces of the structure. 
     As used herein, spatially relative terms, such as “beneath,” “below,” “lower,” “bottom,” “above,” “upper,” “top,” “front,” “rear,” “left,” “right,” and the like, may be used for ease of description to describe one element&#39;s or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. Unless otherwise specified, the spatially relative terms are intended to encompass different orientations of the materials in addition to the orientation depicted in the figures. For example, if materials in the figures are inverted, elements described as “below” or “beneath” or “under” or “on bottom of” other elements or features would then be oriented “above” or “on top of” the other elements or features. Thus, the term “below” can encompass both an orientation of above and below, depending on the context in which the term is used, which will be evident to one of ordinary skill in the art. The materials may be otherwise oriented (e.g., rotated 90 degrees, inverted, flipped) and the spatially relative descriptors used herein interpreted accordingly. 
     As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. 
     As used herein, “and/or” includes any and all combinations of one or more of the associated listed items. 
     As used herein, the term “configured” refers to a size, shape, material composition, and arrangement of one or more of at least one structure and at least one apparatus facilitating operation of one or more of the structure and the apparatus in a pre-determined way. 
     As used herein, the phrase “coupled to” refers to structures operatively connected with each other, such as electrically connected through a direct ohmic connection or through an indirect connection (e.g., via another structure). 
     As used herein, the term “mirrors” means and includes that at least two structures are mirror images of one another. As a non-limiting example, a first staircase structure that mirrors a second staircase structure may exhibit the substantially the same size and substantially the same shape as the second staircase structure, but may outwardly extend in a direction that opposes a direction in which the second structure outwardly extends. The first staircase structure may, for example, exhibit a generally negative slope, and the second staircase structure may exhibit a generally positive slope. 
     As used herein, the term “substantially” in reference to a given parameter, property, or condition means and includes to a degree that one of ordinary skill in the art would understand that the given parameter, property, or condition is met with a degree of variance, such as within acceptable manufacturing tolerances. By way of example, depending on the particular parameter, property, or condition that is substantially met, the parameter, property, or condition may be at least 90.0% met, at least 95.0% met, at least 99.0% met, or even at least 99.9% met. 
     As used herein, the term “about” in reference to a given parameter is inclusive of the stated value and has the meaning dictated by the context (e.g., it includes the degree of error associated with measurement of the given parameter). 
       FIGS.  1 A through  1 G  are simplified perspective ( FIGS.  1 A through  1 F ) and top-down ( FIG.  1 G ) views illustrating embodiments of a method of forming a semiconductor device structure including a staircase structure, such as a memory array structure (e.g., a memory array block) for a 3D non-volatile memory device (e.g., a 3D NAND Flash memory device). With the description provided below, it will be readily apparent to one of ordinary skill in the art that the methods described herein may be used in various devices. In other words, the methods of the disclosure may be used whenever it is desired to form a semiconductor device including a staircase structure. 
     Referring to  FIG.  1 A , a semiconductor device structure  100  may include a stack structure  102  exhibiting an alternating sequence of insulating structures  104  and additional insulating structures  106  arranged in tiers  108 . Each of the tiers  108  may include one of the insulating structures  104  and one of the additional insulating structures  106 . For clarity and ease of understanding of the drawings and related description,  FIG.  1 A  shows the stack structure  102  as including eleven (11) tiers  108  (i.e., tiers  108   a  through  108   k ) of the insulating structures  104  and the additional insulating structures  106 . However, the stack structure  102  may include a different number of tiers  108 . For example, in additional embodiments, the stack structure  102  may include greater than eleven (11) tiers  108  (e.g., greater than or equal to fifteen (15) tiers  108 , greater than or equal to twenty-five (25) tiers  108 , greater than or equal to fifty (50) tiers  108 , greater than or equal to one hundred (100) tiers  108 ) of the insulating structures  104  and the additional insulating structures  106 , or may include less than eleven (11) tiers  108  (e.g., less than or equal to ten (10) tiers  108 , less than or equal to five (5) tiers  108 , less than or equal to three (3) tiers  108 ) of the insulating structures  104  and the additional insulating structures  106 . 
     The insulating structures  104  may be formed of and include at least one insulating material, such as one or more of an oxide material (e.g., silicon dioxide, phosphosilicate glass, borosilicate glass, borophosphosilicate glass, fluorosilicate glass, titanium dioxide, zirconium dioxide, hafnium dioxide, tantalum oxide, magnesium oxide, aluminum oxide, or a combination thereof), a nitride material (e.g., silicon nitride), an oxynitride material (e.g., silicon oxynitride), and amorphous carbon. Each of the insulating structures  104  may independently include a substantially homogeneous distribution or a substantially heterogeneous distribution of the at least one insulating material. In some embodiments, each of the insulating structures  104  exhibits a substantially homogeneous distribution of insulating material. In additional embodiments, at least one of the insulating structures  104  exhibits a substantially heterogeneous distribution of at least one conductive material. One or more of the insulating structures  104  may, for example, be formed of and include a stack (e.g., laminate) of at least two different insulating materials. In some embodiments, each of the insulating structures  104  is formed of and includes silicon dioxide. The insulating structures  104  may each be substantially planar, and may each independently exhibit any desired thickness. In addition, each of the insulating structures  104  may be substantially the same (e.g., exhibit substantially the same material composition, material distribution, size, and shape) as one another, or at least one of the insulating structures  104  may be different (e.g., exhibit one or more of a different material composition, a different material distribution, a different size, and a different shape) than at least one other of the insulating structures  104 . In some embodiments, each of the insulating structures  104  is substantially the same as each other of the insulating structures  104 . 
     The additional insulating structures  106  may each be formed of and include at least one additional insulating material that may be selectively removable relative to the insulating material of the insulating structures  104 . The at least one additional insulating material of the additional insulating structures  106  may be different than the insulating material of the insulating structures  104 , and may comprise one or more of an oxide material (e.g., silicon dioxide, phosphosilicate glass, borosilicate glass, borophosphosilicate glass, fluorosilicate glass, titanium dioxide, zirconium dioxide, hafnium dioxide, tantalum oxide, magnesium oxide, aluminum oxide, or combinations thereof), a nitride material (e.g., silicon nitride), an oxynitride material (e.g., silicon oxynitride), and amorphous carbon. Each of the additional insulating structures  106  may independently include a substantially homogeneous distribution or a substantially heterogeneous distribution of the at least one additional insulating material. In some embodiments, each of the additional insulating structures  106  exhibits a substantially homogeneous distribution of additional insulating material. In further embodiments, at least one of the additional insulating structures  106  exhibits a substantially heterogeneous distribution of at least one conductive material. One or more of the additional insulating structures  106  may, for example, be formed of and include a stack (e.g., laminate) of at least two different additional insulating materials. In some embodiments, each of the additional insulating structures  106  is formed of and includes silicon nitride. The additional insulating structures  106  may each be substantially planar, and may each independently exhibit any desired thickness. In addition, each of the additional insulating structures  106  may be substantially the same (e.g., exhibit substantially the same material composition, material distribution, size, and shape) as one another, or at least one of the additional insulating structures  106  may be different (e.g., exhibit one or more of a different material composition, a different material distribution, a different size, and a different shape) than at least one other of the additional insulating structures  106 . In some embodiments, each of the additional insulating structures  106  is substantially the same as each other of the additional insulating structures  106 . The additional insulating structures  106  may serve as sacrificial structures for the subsequent formation of conductive structures, as described in further detail below. 
     As shown in  FIG.  1 A , in some embodiments, the alternating sequence of the insulating structures  104  and the additional insulating structures  106  begins with one of the insulating structures  104 . In additional embodiments, the insulating structures  104  and the additional insulating structures  106  exhibit a different arrangement relative to one another. By way of non-limiting example, the insulating structures  104  and the additional insulating structures  106  may be arranged in an alternating sequence beginning with one of the additional insulating structures  106 . In some embodiments, each of the tiers  108  includes one of the additional insulating structures  106  on or over one of the insulating structures  104 . In additional embodiments, each of the tiers  108  includes one of the insulating structures  104  on or over one of the additional insulating structures  106 . 
     The stack structure  102 , including the each of the tiers  108  thereof, may be formed using conventional processes (e.g., conventional deposition processes, conventional material removal processes) and conventional processing equipment, which are not described in detail herein. By way of non-limiting example, the insulating structures  104  and the additional insulating structures  106  may be formed through one or more of in situ growth, spin-on coating, blanket coating, chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition (PECVD), atomic layer deposition (ALD), and physical vapor deposition (PVD). 
     Referring next to  FIG.  1 B , a masking structure  110  may be formed on or over the stack structure  102 . The masking structure  110  may be formed of and include at least one material (e.g., at least one hard mask material) suitable for use as an etch mask to pattern portions of the stack structure  102  (e.g., portions of the tiers  108 , including portions of the insulating structures  104  and portions of the additional insulating structures  106 , remaining uncovered by the masking structure  110 ) to form at least one staircase structure, as described in further detail below. By way of non-limiting example, the masking structure  110  may be formed of and include at least one of amorphous carbon, silicon, a silicon oxide, a silicon nitride, a silicon oxycarbide, aluminum oxide, and a silicon oxynitride. The masking structure  110  may be homogeneous (e.g., may comprise a single material layer), or may be heterogeneous (e.g., may comprise a stack exhibiting at least two different material layers). 
     The position and dimensions of the masking structure  110  may be selected at least partially based on desired positions and desired dimensions of one or more staircase structures to be subsequently formed in the stack structure  102 . By way of non-limiting example, as shown in  FIG.  1 B , the masking structure  110  may be centrally positioned on or over the stack structure  102  in the Y-direction, may have a width W 2  less than the width W 1  of the stack structure  102 , and may have substantially the same length L 1  as the stack structure  102 . Widths of portions of the stack structure  102  remaining uncovered by (e.g., not underlying) the masking structure  110  may correspond to widths of the one or more staircase structures to be subsequently formed in the stack structure  102 . In additional embodiments, the masking structure  110  may exhibit one or more of a different position (e.g., a different position in one or more of the X-direction and the Y-direction), a different width W 2 , and a different length (e.g., a length less than the length L 1 ). As a non-limiting example, the masking structure  110  may be centrally positioned on or over the stack structure  102  in each of the Y-direction and the X-direction, may have a width W 2  less than the width W 1  of the stack structure  102 , and may have a length less than the length L 1  of the stack structure  102 . As another non-limiting example, the masking structure  110  may be non-centrally positioned over the stack structure  102  in the Y-direction, may have a width W 2  less than the width W 1  of the stack structure  102 , and may have substantially the same length L 1  as the stack structure  102 . The masking structure  110  may be formed on or over the stack structure  102  to any desired thickness. 
     The masking structure  110  may be formed using conventional processes (e.g., conventional deposition processes, such as at least one of in situ growth, spin-on coating, blanket coating, CVD, PECVD, ALD, and PVD, conventional photolithography processes, conventional material removal processes) and conventional processing equipment, which are not described in detail herein. 
     Referring to next to  FIG.  1 C , portions of the stack structure  102  ( FIG.  1 B ) (e.g., portions of one or more of the tiers  108 ) remaining uncovered by the masking structure  110  may be subjected to at least one material removal process (e.g., one or more of a trimming process and a chopping process) to form a modified stack structure  112 . The modified stack structure  112  may include one or more staircase structures  114  each independently formed of and including one or more steps  116 . The steps  116  of the one or more staircase structures  114  may be at least partially defined by exposed portions of one or more of the tiers  108  remaining following the at least one material removal process. 
     The modified stack structure  112  may include a single (e.g., only one) staircase structure  114 , or may include multiple (e.g., more than one) staircase structures  114 . In some embodiments, the modified stack structure  112  includes multiple staircase structures  114 . By way of non-limiting example, as shown in  FIG.  1 C , the modified stack structure  112  may include one or more so-called stadium structures  118  each including opposing staircase structures  114 . A first stadium structure  118   a  may be positioned along one side of the masking structure  110 , and a second stadium structure  118   b  may be positioned along an opposing side of the masking structure  110 . The first stadium structure  118   a  may include a first forward staircase structure  114   a , and a first reverse staircase structure  114   b  that mirrors the first forward staircase structure  114   a . The second stadium structure  118   b  may extend parallel to the first stadium structure  118   a  (e.g., the first stadium structure  118   a  and the second stadium structure  118   b  may both extend in the X-direction), and may include a second forward staircase structure  114   c , and a second reverse staircase structure  114   d  that mirrors the second forward staircase structure  114   c . The first stadium structure  118   a  and the second stadium structure  118   b  may be substantially similar to one another (e.g., may exhibit substantially the same shapes and sizes as one another), or may be different than one another (e.g., may exhibit one or more of different shapes and different sizes than one another). In some embodiments, the first stadium structure  118   a  and the second stadium structure  118   b  are substantially similar to one another. The first stadium structure  118   a  and the second stadium structure  118   b  may serve as redundant and/or alternative means of connecting to one or more of the tiers  108  of the modified stack structure  112 , as may the opposing staircase structures (e.g., the first forward staircase structure  114   a  and the first reverse staircase structure  114   b  of the first stadium structure  118   a , and/or the second forward staircase structure  114   c  and the second reverse staircase structure  114   d  of the second stadium structure  118   b ) of one or more of the first stadium structure  118   a  and the second stadium structure  118   b.    
     In additional embodiments, the modified stack structure  112  may exhibit one or more of a different number and different configuration of the staircase structures  114 . By way of non-limiting example, the modified stack structure  112  may include only one (1) stadium structure  118  (e.g., only the first stadium structure  118   a , or only the second stadium structure  118   b ), may include more than two (2) stadium structures  118  extending parallel to one another, may include two or more stadium structures  118  extending in series with one another, may include one or more forward staircase structures (e.g., one or more of the first forward staircase structure  114   a  and the second forward staircase structure  114   c ) but not one or more reverse staircase structures (e.g., one or more of the first reverse staircase structure  114   b  and the second reverse staircase structure  114   d  may be omitted), may include one or more reverse staircase structures (e.g., one or more of the first reverse staircase structure  114   b  and the second reverse staircase structure  114   d ) but not one or more forward staircase structures (e.g., one or more of the first forward staircase structure  114   a  and the second forward staircase structure  114   c  may be omitted), may include two or more forward staircase structures extending in series with one another, and/or may include two or more reverse staircase structures extending in series with one another. 
     Each of the staircase structures  114  included in the modified stack structure  112  may independently include a desired number of steps  116 . The number of steps  116  included in each of the staircase structures  114  may be substantially the same as (e.g., equal to) or may be different than (e.g., less than, or greater than) the number of tiers  108  in the modified stack structure  112 . In some embodiments, the number of steps  116  included in each of the staircase structures  114  is less than the number of tiers  108  in the modified stack structure  112 . As a non-limiting example, as shown in  FIG.  1 C , each of the staircase structures  114  (e.g., the first forward staircase structure  114   a , the first reverse staircase structure  114   b , the second forward staircase structure  114   c , and the second reverse staircase structure  114   d ) may include ten (10) steps  116  at least partially defined by ends of the eleven (11) tiers  108  (e.g., tiers  108   a  through  108   k ) of the modified stack structure  112 . In additional embodiments, one or more of the staircase structures  114  may include a different number of steps  116  (e.g., less than ten (10) steps  116 , greater than ten (10) steps  116 ). By way of non-limiting example, if the modified stack structure  112  includes eleven (11) tiers  108 , at least one of the staircase structures  114  may include five (5) steps  116  at least partially defined by ends of a relatively lower group of the tiers  108  (e.g., tier  108   f  through tier  108   k ), and at least one other of the staircase structures  114  may include five (5) steps  116  at least partially defined by ends of a relatively higher group of the tiers  108  (e.g., tiers  108   a  through  108   e ). 
     The dimensions of each of the steps  116  may independently be tailored to desired dimensions and positions of additional structures (e.g., conductive structures, conductive contact structures) and/or openings (e.g., slots) to be formed in, on, over, and/or adjacent to the steps  116  during subsequent processing of the semiconductor device structure  100 , as described in further detail below. In some embodiments, each of the steps  116  exhibits substantially the same dimensions (e.g., substantially the same width, substantially the same length, and substantially the same height) as each other of the steps  116 . In additional embodiments, at least one of the steps  116  exhibits different dimensions (e.g., one or more of a different width, a different length, and a different height) than at least one other of the steps  116 . 
     The staircase structures  114  may be formed using conventional processes (e.g., conventional photolithography processes, conventional material removal processes) and conventional processing equipment, which are not described in detail herein. By way of non-limiting example, a photoresist structure may be formed on or over at least uncovered portions of the stack structure  102  ( FIG.  1 B ), the photoresist structure may be photolithographically processed (e.g., photoexposed and developed) to remove at least one width thereof, one or more of the tiers  108  may be etched (e.g., anisotropically etched, such as anisotropically dry etched) using the masking structure  110  and remaining portions of the photoresist structure as etching masks, the photoresist structure may be subjected to additional photolithographic processing to remove at least one additional width thereof, at least another group of the tiers  108  (e.g., previously etched tiers  108  and one or more additional tiers  108 ) may be etched using the masking structure  110  and newly remaining portions of the photoresist structure as etching masks, and so on, until the modified stack structure  112  including the one or more staircase structures  114  is formed. 
     Referring next to  FIG.  1 D , the masking structure  110  ( FIG.  1 C ) may be removed, and one or more openings  120  (e.g., slots, apertures, slits) may be formed in the modified stack structure  112 . The masking structure  110  may be removed using one or more conventional material removal processes, which are not described in detail herein. By way of non-limiting example, the masking structure  110  may be selectively removed through at least one conventional etching process (e.g., a conventional wet etching process, a conventional dry etching process). 
     The openings  120  may longitudinally extend (e.g., in the Z-direction) through (e.g., completely through) the modified stack structure  112 , may be positioned laterally inward (e.g., in the Y-direction) of the staircase structures  114 , and may continuously laterally extend (e.g., in the X-direction) across the entire lengths of the staircase structures  114 . By way of non-limiting example, as shown in  FIG.  1 D , the openings  120  may extend completely through each of the tiers  108 , may be positioned laterally inwardly adjacent the stadium structures  118 , and may continuously laterally extend across the entire lengths of the stadium structures  118 . A first opening  120   a  may be positioned laterally between (e.g., in the Y-direction) the first stadium structure  118   a  and a remaining middle section  122  of the modified stack structure  112 , and may laterally extend (e.g., in the X-direction) from a top (e.g., a laterally inward end of tier  108   a ) of the first forward staircase structure  114   a  to a top (e.g., an opposing laterally inward end of tier  108   a ) of the first reverse staircase structure  114   b . A second opening  120   b  may be positioned laterally between (e.g., in the Y-direction) the second stadium structure  118   b  and the remaining middle section  122  of the modified stack structure  112 , and may laterally extend parallel (e.g., in the X-direction) to the first opening  120   a  from a top (e.g., a laterally inward end of tier  108   a ) of the second forward staircase structure  114   c  to a top (e.g., an opposing laterally inward end of tier  108   a ) of the second reverse staircase structure  114   d.    
     In additional embodiments, one or more of the openings  120  may exhibit a different configuration than that depicted in  FIG.  1 D . As a non-limiting example, in embodiments wherein the modified stack structure  112  includes at least one forward staircase structure (e.g., the first forward staircase structure  114   a , and/or the second forward staircase structure  114   c ) but not at least one reverse staircase structure (e.g., not at least one of the first reverse staircase structure  114   b  and the second reverse staircase structure  114   d ) opposing the forward staircase structure, the opening  120  may be positioned laterally inward (e.g., laterally adjacent) the forward staircase structure and may longitudinally extend completely through the tiers  108 , but may continuously laterally extend from a top (e.g., a laterally inward end of the tier  108   a ) of the forward staircase structure to a bottom (e.g., as defined by one or more of the tier  108   k  and the tier  108   j ) of the forward staircase structure. As another non-limiting example, in embodiments wherein the modified stack structure  112  includes at least one reverse staircase structure (e.g., the first reverse staircase structure  114   b , and/or the second reverse staircase structure  114   d ) but not at least one forward staircase structure (e.g., not at least one of the first forward staircase structure  114   a  and the second forward staircase structure  114   c ) opposing the reverse staircase structure, the opening  120  may be positioned laterally inward (e.g., laterally adjacent) the reverse staircase structure and may longitudinally extend completely through the tiers  108 , but may continuously laterally extend from a bottom (e.g., as defined by one or more of the tier  108   k  and the tier  108   j  and) of the reverse staircase structure to a top (e.g., a laterally inward end of the tier  108   a ) of the reverse staircase structure. 
     Any desired number (e.g., quantity, amount) of openings  120  may be formed in the modified stack structure  112 . The number of openings  120  may correspond to desired configurations (e.g., shapes, sizes, positions) of conductive structures to be formed in the modified stack structure  112  through subsequent processing acts, as described in further detail below. A single (e.g., only one) opening  120  may be formed laterally inward (e.g., in the Y-direction) of the staircase structures  114  and may continuously laterally extend across and between (e.g., in the X-direction) the staircase structures  114 , or multiple (e.g., more than one) openings  120  may be formed laterally inward (e.g., in the Y-direction) of the staircase structures  114  and may continuously laterally extend in parallel across and between (e.g., in the X-direction) the staircase structures  114 . As shown in  FIG.  1 D , in some embodiments, two (2) openings  120  (e.g., the first opening  120   a , and the second opening  120   b ) are formed in the modified stack structure  112 . The two (2) openings  120  may be disposed between the stadium structures  118  (e.g., the first stadium structure  118   a , and the second stadium structure  118   b ) of the modified stack structure  112 , and may flank opposing sides of the remaining middle section  122  of the modified stack structure  112 . In additional embodiments, more than two (2) openings  120  are formed in the modified stack structure  112 . For example, at least one additional opening (e.g., a third opening) may be formed in the remaining middle section  122  of the modified stack structure  112  (e.g., laterally between the first opening  120   a  and the second opening  120   b ). The at least one additional opening may extend completely longitudinally through the remaining middle section  122  of the modified stack structure  112 , and may continuously laterally extend across the remaining middle section  122  in parallel to the other openings  120  (e.g., the first opening  120   a , and the second opening  120   b ). 
     The dimensions and spacing of the one or more openings  120  may be selected to provide desired dimensions (e.g., widths) to and/or maintain desired dimensions of the staircase structures  114  (including the steps  116  thereof), and to provide desired dimensions (e.g., widths), continuity, and spacing to conductive structures to be formed using the openings  120 , as described in further detail below. If more than one opening  120  is formed in the modified stack structure  112 , each of the openings  120  may exhibit substantially the same dimensions (e.g., substantially the same width, substantially the same length, and substantially the same height), or at least one of the openings  120  may exhibit one or more different dimensions (e.g., a different width, a different length, and/or a different height) than at least one other of the openings  120 . In some embodiments, each of the openings  120  exhibits substantially the same dimensions. In addition, if more than two (2) openings  120  are formed in the modified stack structure  112 , adjacent openings  120  may be substantially uniformly (e.g., evenly) spaced apart from one another, or may be non-uniformly (non-evenly) spaced apart from one another. In some embodiments, adjacent openings  120  are substantially uniformly spaced apart from one another. The openings  120  may be symmetrically distributed across the modified stack structure  112 , or may be asymmetrically distributed across the modified stack structure  112 . 
     The openings  120  may be formed in the modified stack structure  112  using at least one conventional material removal processes, which is not described in detail herein. For example, one or more portions of the modified stack structure  112  may be subjected to at least one etching process (e.g., at least one dry etching process, such as at least one of a reactive ion etching (RIE) process, a deep RIE process, a plasma etching process, a reactive ion beam etching process, and a chemically assisted ion beam etching process; at least one wet etching process, such as at least one of a hydrofluoric acid etching process, a buffered hydrofluoric acid etching process, and a buffered oxide etching process) to form the openings  120  in the modified stack structure  112 . The material removal process may remove one or more portions of the staircase structures  114  (e.g., so as to reduce widths of the staircase structures  114 ), and/or may remove one or more portions of the modified stack structure  112  previously covered by the masking structure  110  ( FIG.  1 C ). 
     Referring next to  FIG.  1 E , portions of the additional insulating structures  106  ( FIG.  1 D ) may be selectively removed, and may be replaced with a conductive material to form a conductive stack structure  124 . As shown in  FIG.  1 E , each of the tiers  108  of the conductive stack structure  124  may include one or more conductive structures  126  (e.g., conductive gates, conductive plates) extending (e.g., in the X-direction and/or in the Y-direction) into lateral surfaces thereof. The one or more conductive structures  126  of each tier  108  of the conductive stack structure  126  may at least partially (e.g., substantially) laterally surround remaining portions  128  (e.g., unremoved portions) of the additional insulating structures  106 . 
     The conductive structures  126  may follow (e.g., route along) lateral (e.g., side) surfaces of the conductive stack structure  124 . For example, the conductive structures  126  may extend into and along outer lateral surfaces (e.g., peripheral lateral surfaces) of the tiers  108 , as well as into and along inner lateral surfaces of the tiers  108  (e.g., lateral surfaces at least partially defined by the openings  120  longitudinally extending through the tiers  108 ). For each of the tiers  108 , the conductive structures  126  may laterally extend to and around each of the openings  120  (e.g., completely around ends of the openings  120 , and completely across the portions of the middle section  122  of the conductive stack structure  124  adjacent the openings  120 ) to form one or more continuous conductive paths between a first end  130  of the conductive stack structure  124  and a second, opposing end  132  of the conductive stack structure  124 . The first end  130  and the second, opposing end  132  of the conductive stack structure  124  may each be coupled to other components of a semiconductor device (e.g., a memory device) including the semiconductor device structure  100 , such as one or more memory cell arrays (e.g., vertical memory cell arrays). In addition, portions of at least some of the conductive structures  126  may laterally extend (e.g., in the X-direction) to and at least partially define the staircase structures  114  of the conductive stack structure  124  to form conductive contact regions (e.g., landing pad regions) for at least some of the tiers  108 . For each of the conductive structures  126 , portions thereof laterally extending to and at least partially defining one or more of the staircase structures  114  may be integral and continuous with other portions thereof laterally extending to and around the openings  120  positioned laterally inward of (e.g., laterally inwardly adjacent) the staircase structures  114 . Furthermore, in tiers  108  longitudinally below the staircase structures  114  (e.g., untrimmed tiers  108  and/or unchopped tiers  108 ), the conductive structures  126  thereof may laterally extend to and may completely surround the openings  120 . 
     In some embodiments, the conductive stack structure  124  includes multiple (e.g., more than one) conductive structures  126  in one or more (e.g., each) of the tiers  108  thereof. By way of non-limiting example, as shown in  FIG.  1 E , each of the one or more tiers  108  may include one conductive structure  126  at least partially defining the first stadium structure  118   a  and surrounding sides of the first opening  120   a , and may also include an additional conductive structure  126  at least partially defining the second stadium structure  118   b  and surrounding sides of the second opening  120   b . The conductive structures  126  associated with the first stadium structure  118   a  and the first opening  120   a  may each extend laterally inward from the first end  130  and the second, opposing end  132  of the conductive stack structure  124  along outer lateral surfaces of the conductive stack structure  124  to the first stadium structure  118   a , wherein portions of each of the conductive structures  126  may at least partially define the first stadium structure  118   a  (e.g., including the first forward staircase structure  114   a  and the first reverse staircase structure  114   b ) and other portions of each of the conductive structures  126  may extend around inner lateral surfaces of the conductive stack structure  124  at least partially defined by the first opening  120   a . The additional conductive structures  126  associated with the second stadium structure  118   b  and the second opening  120   b  may each extend laterally inward from the first end  130  and the second, opposing end  132  of the conductive stack structure  124  along other outer lateral surfaces of the conductive stack structure  124  to the second stadium structure  118   b , wherein portions of each of the additional conductive structures  126  may at least partially define the second stadium structure  118   b  (e.g., including the second forward staircase structure  114   c  and the second reverse staircase structure  114   d ) and other portions of each of the additional conductive structures  126  may extend around inner lateral surfaces of the conductive stack structure  124  at least partially defined by the second opening  120   b . For each of the tiers  108 , the multiple conductive structures  126  may be separated (e.g., isolated) from one another by the remaining portion  128  of the additional insulating structure  106  ( FIG.  1 D ). For example, as shown in  FIG.  1 E , for each of the different tiers  108  (e.g., each of the tiers  108   a  through  108   k ) of the conductive stack structure  124 , a conductive structure  126  associated with the first stadium structure  118   a  and the first opening  120   a  may be separated from an additional conductive structure  126  associated with the second stadium structure  118   b  and the second opening  120   b  by the remaining portion  128  of the additional insulating structure  106 . 
     In additional embodiments, the conductive stack structure  124  includes a single (e.g., only one) conductive structure  126  in one or more (e.g., each) of the tiers  108  thereof. The single conductive structure  126  of each of the one or more tiers  108  may at least partially define each of the staircase structures  114 , and may surround sides of each of the openings  120 . For each of the one or more tiers  108 , all portions of the single conductive structure  126  thereof may be integral and continuous with one another, and may form a continuous conductive path extending from the first end  130  of the conductive stack structure  124  to the second, opposing end  132  of the of the conductive stack structure  124 . By way of non-limiting example, in embodiments wherein the conductive stack structure  124  includes at least one additional opening laterally between the first opening  120   a  and the second opening  120   b , each of the tiers  108  may include a single conductive structure  126  at least partially defining each of the first stadium structure  118   a  and the second stadium structure  118   b  and surrounding sides of each of the first opening  120   a , the second opening  120   b , and the at least one additional opening. The single conductive structure  126  may extend laterally inward from the first end  130  and the second, opposing end  132  of the conductive stack structure  124  along outer lateral surfaces of the conductive stack structure  124  to each of the first stadium structure  118   a  and the second stadium structure  118   b , wherein portions of the single conductive structure  126  may extend into and at least partially define the first stadium structure  118   a  (e.g., including the first forward staircase structure  114   a  and the first reverse staircase structure  114   b ) and second stadium structure  118   b  (e.g., including the second forward staircase structure  114   c  and the second reverse staircase structure  114   d ) and other portions of the single conductive structure  126  may extend around inner lateral surfaces of the tier  108  at least partially defined by one or more of the first opening  120   a , the second opening  120   b , and the additional opening. In such embodiments, the remaining portions  128  of the additional insulating structure  106  ( FIG.  1 D ) laterally intervening between the first opening  120   a  and the second opening  120   b  may be absent (e.g., omitted) from the conductive stack structure  124 . 
     The dimensions and shapes of the conductive structures  126  may directly correspond to the dimensions and shapes of the removed portions of the additional insulating structures  106  ( FIG.  1 D ). A width (e.g., lateral depth within the conductive stack structure  124 ) of each of the conductive structures  126  may be substantially uniform across the entire path (e.g., route) of the conductive structure  126 , or the width of at least one of the conductive structures  126  may be substantially non-uniform (e.g., variable) across different portions of the path of the conductive structure  126 . In addition, each of the conductive structures  126  may exhibit a different shape and at least one different dimension than each other of the conductive structures  126 , or at least one of the conductive structures  126  may exhibit one or more of substantially the same shape and substantially the same dimensions as at least one other of the conductive structures  126 . By way of non-limiting example, as shown in  FIG.  1 E , conductive structures  126  of different tiers  108  may exhibit different shapes and different dimensions (e.g., different lengths associated with the locations of the different steps  116  of the staircase structures  114 ) than one another, but conductive structures  126  within the same tier  108  may exhibit substantially the same shapes and substantially the same dimensions as one another (e.g., conductive structures  126  within the same tier  108  may be mirror images of one another). In additional embodiments, conductive structures  126  of two or more different tiers  108  may exhibit substantially the same shapes and substantially the same dimensions as one another. In further embodiments, conductive structures  126  within the same tier  108  may exhibit one or more of a different shape and at least one different dimension than one another. 
     The conductive structures  126  may be formed of and include at least one conductive material, such as a metal, a metal alloy, a conductive metal oxide, a conductive metal nitride, a conductive metal silicide, a conductively-doped semiconductor material, or combinations thereof. By way of non-limiting example, the conductive structures  126  may be formed of and include at least one of tungsten (W), tungsten nitride (WN), nickel (Ni), tantalum (Ta), tantalum nitride (TaN), tantalum silicide (TaSi), platinum (Pt), copper (Cu), silver (Ag), gold (Au), aluminum (Al), molybdenum (Mo), titanium (Ti), titanium nitride (TiN), titanium silicide (TiSi), titanium silicon nitride (TiSiN), titanium aluminum nitride (TiAlN), molybdenum nitride (MoN), iridium (Ir), iridium oxide (IrOx), ruthenium (Ru), ruthenium oxide (RuO x ), and conductively-doped silicon. In some embodiments, the conductive structures  126  are formed of and include W. 
     The conductive structures  126  may be formed by selectively removing portions of the additional insulating structures  106  ( FIG.  1 D ) relative to the insulating structures  104  to form recessed regions laterally extending into each of the tiers  108 , and then at least partially (e.g., substantially) filling the recessed regions with at least one conductive material. The recessed regions may be formed by subjecting the modified stack structure  112  ( FIG.  1 D ) to at least one etching processing (e.g., an isotropic etching process) employing an etch chemistry in which the insulative material of the additional insulating structures  106  ( FIG.  1 D ) is selectively removed relative to that of the insulating structures  104 . By way of non-limiting example, if the insulating structures  104  are formed of and include silicon dioxide (SiO 2 ), and the additional insulating structures  106  are formed of and include silicon nitride (Si 3 N 4 ), the modified stack structure  112  may be exposed to an etchant comprising phosphoric acid (H 3 O 4 P) to selectively remove portions of the additional insulating structures  106  adjacent exposed lateral surfaces (e.g., exposed outer lateral surfaces, exposed inner lateral surfaces at least partially defined by the openings  120 ) of the modified stack structure  112 . Thereafter, the conductive material may be formed (e.g., delivered, deposited) within recessed regions to form the conductive structures  126 . 
     In additional embodiments, rather than selectively removing and replacing portions of the additional insulating structures  106  ( FIG.  1 D ) to form the conductive stack structure  124 , portions of the insulating structures  104  may instead be selectively removed and replaced with conductive material to form a conductive stack structure. Aside from the sequence (e.g., order) of the alternating conductive structures and insulating structures of such a conductive stack structure and differences (if any) associated with material properties of the insulating structures  104  as compared to those of the additional insulating structures  106 , such a conductive stack structure may be substantially similar to and may have little or no difference in terms of functionality and/or operability as compared to the conductive stack structure  124  depicted in  FIG.  1 E . 
     Referring next to  FIG.  1 F , conductive contact structures  134  (e.g., conductive plugs, conductive vertical interconnects) may be formed on, over, and/or within the one or more of staircase structures  114  of the conductive stack structure  124 , and conductive routing structures  136  (e.g., conductive interconnects, conductive bridges) may be formed to electrically connect the conductive contact structures  134  to at least one string driver device  138 .  FIG.  1 G  is a top-down view of the semiconductor device structure  100  at the processing stage depicted in  FIG.  1 F . 
     The conductive contact structures  134  may be coupled to the conductive structures  126  of the tiers  108  of the conductive stack structure  124  at the steps  116  of the staircase structures  114 . Each of the tiers  108  (e.g., each of the tiers  108   a  through  108   k ) may have one or more of the conductive contact structures  134  coupled to the conductive structure(s)  126  thereof, or less than all of the tiers  108  (e.g., less than all of the tiers  108   a  through  108   k , such as only tiers  108   b  through  108   j ) may have one or more of the conductive contact structures  134  coupled to the conductive structure(s)  126  thereof. Each of the tiers  108  including one or more of the conductive contact structures  134  coupled to the conductive structure(s)  126  thereof may include a single (e.g., only one) conductive contact structure  134  coupled to the conductive structure(s)  126  thereof, or may include multiple (e.g., more than one) conductive contact structures  134  coupled thereto. As a non-limiting example, as shown in  FIG.  1 F , in embodiments wherein each of the tiers  108  includes multiple conductive structures  126  (e.g., multiple conductive structures  126  laterally isolated from one another by the remaining portion  128  of one of the additional insulating structures  106  ( FIG.  1 D )), each conductive structure  126  of a given tier  108  may have at least one of the conductive contact structures  134  coupled thereto at one or more of the steps  116  (e.g., one or more of the steps  116  of the first stadium structure  118   a , one or more of the steps  116  of the second stadium structure  118   b ) at least partially defined by the conductive structure  126 . As another non-limiting example, in embodiments wherein each of the tiers  108  includes a single (e.g., only one) conductive structure  126 , the single conductive structure  126  may have at least one of the conductive contact structures  134  coupled thereto at one or more of the steps  116  at least partially defined by the single conductive structure  126 . 
     The conductive contact structures  134  may be formed on or over a single (e.g., only one) staircase structure  114  of the conductive stack structure  124 , or may be formed on or over multiple (e.g., more than one) staircase structures  114  of the conductive stack structure  124 . By way of non-limiting example, as shown in  FIGS.  1 F and  1 G , within at least one of the stadium structures  118  (e.g., at least one of the first stadium structure  118   a  and the second stadium structure  118   b ) of the conductive stack structure  124 , a portion of the conductive contact structures  134  may be formed on or over a forward staircase structure (e.g., the first forward staircase structure  114   a , the second forward staircase structure  114   c ) and an additional portion of the conductive contact structures  134  may be formed on or over a reverse staircase structure (e.g., the first reverse staircase structure  114   b , the second reverse staircase structure  114   d ). In additional embodiments, within at least one of the stadium structures  118 , each of the conductive contact structures  134  may be formed on or over a forward staircase structure (e.g., the first forward staircase structure  114   a , the second forward staircase structure  114   c ). In further embodiments, within at least one of the stadium structures  118 , each of the conductive contact structures  134  may be formed on or over a reverse staircase structure (e.g., the first reverse staircase structure  114   b , the second reverse staircase structure  114   d ). 
     Conductive contact structures  134  formed on or over the same staircase structure  114  (e.g., one of the first forward staircase structure  114   a , the first reverse staircase structure  114   b , the second forward staircase structure  114   c , and the second reverse staircase structure  114   d ) may be substantially uniformly (e.g., evenly) spaced apart from one another, or may be non-uniformly (e.g., unevenly) spaced apart from one another. Conductive contact structures  134  formed on or over the same staircase structure  114  may be formed to be generally centrally positioned (e.g., in at least the X-direction) on or over the steps  116  associated therewith. Accordingly, distances between adjacent conductive contact structures  134  located on or over the same staircase structure  114  may vary in accordance with variance in the lengths (e.g., in the X-direction) of the adjacent steps  116  associated with the adjacent conductive contact structures  134 . In addition, conductive contact structures  134  formed on or over the same staircase structure  114  may be substantially aligned with one another (e.g., not offset from one another in the Y-direction), or may be at least partially non-aligned with one another (e.g., offset from one another in the Y-direction). 
     The conductive contact structures  134  may be formed of and include at least one conductive material, such as a metal (e.g., tungsten, titanium, molybdenum, niobium, vanadium, hafnium, tantalum, chromium, zirconium, iron, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium, platinum, copper, silver, gold, aluminum), a metal alloy (e.g., a cobalt-based alloy, an iron-based alloy, a nickel-based alloy, an iron- and nickel-based alloy, a cobalt- and nickel-based alloy, an iron- and cobalt-based alloy, a cobalt- and nickel- and iron-based alloy, an aluminum-based alloy, a copper-based alloy, a magnesium-based alloy, a titanium-based alloy, a steel, a low-carbon steel, a stainless steel), a conductive metal-containing material (e.g., a conductive metal nitride, a conductive metal silicide, a conductive metal carbide, a conductive metal oxide), a conductively-doped semiconductor material (e.g., conductively-doped silicon, conductively-doped germanium, conductively-doped silicon germanium), or combinations thereof. Each of the conductive contact structures  134  may have substantially the same material composition, or at least one of the conductive contact structures  134  may have a different material composition than at least one other of the conductive contact structures  134 . 
     With continued reference to  FIG.  1 F , the conductive routing structures  136  may be coupled (e.g., attached, connected) to the conductive contact structures  134  and at least one string driver device  138 . The string driver device  138  may be formed of and include a plurality of switching devices (e.g., transistors). Suitable designs and configurations for the at least one string driver device  138  are well known in the art, and are therefore not described in detail herein. The string driver device  138  may, for example, underlie one or more portions (e.g., central portions, peripheral portions, combinations thereof) of the conductive stack structure  124 . The combination of the conductive contact structures  134  and the conductive routing structures  136  may electrically connect the conductive structures  126  of one or more of the tiers  108  to the string driver device  138 , facilitating application of voltages to the conductive structures  126  using the string driver device  138 . The continuous conductive paths across the conductive stack structure  124  (e.g., from the first end  130  to the second, opposing end  132 ) provided by the configurations of the conductive structures  126  may permit an individual (e.g., single) switching device (e.g., transistor) of the string driver device  138  to drive voltages completely across (e.g., from the first end  130  to the second, opposing end  132 ) and/or in opposing directions across (e.g., toward the first end  130  and toward the second, opposing end  132 ) an individual tier  108  electrically connected thereto. 
     The conductive routing structures  136  may extend from the conductive contact structures  134 , over one or more sections of the conductive stack structure  124 , through one or more additional sections of the conductive stack structure  124 , and to one or more of the string driver devices  138 . By way of non-limiting example, as shown in  FIG.  1 F , the conductive routing structures  136  may extend from conductive contact structures  134 , laterally over the middle section  122  of the conductive stack structure  124 , longitudinally through insulating sections of the tiers  108  including the remaining portions  128  of the additional insulating structures  106  ( FIG.  1 D ) and portions of the insulating structures  104 , and to one or more of the string driver devices  138 . In addition, each of the conductive routing structures  136  may extend to the same string driver device  138 , or at least one of the conductive routing structures  136  may extend to a different string driver device  138  than at least one other of the conductive routing structures  136 . 
     The conductive routing structures  136  may be formed of and include at least one conductive material, such as a metal (e.g., W, Ti, Mo, Nb, V, Hf, Ta, Cr, Zr, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Al), a metal alloy (e.g., a Co-based alloy, an Fe-based alloy, a Ni-based alloy, an Fe- and Ni-based alloy, a Co- and Ni-based alloy, an Fe- and Cu-based alloy, a Co- and Ni- and Fe-based alloy, an Al-based alloy, a Cu-based alloy, a Mg-based alloy, a Ti-based alloy, a steel, a low-carbon steel, a stainless steel), a conductive metal-containing material (e.g., a conductive metal nitride, a conductive metal silicide, a conductive metal carbide, a conductive metal oxide), a conductively-doped semiconductor material (e.g., conductively-doped silicon, conductively-doped germanium, conductively-doped silicon germanium), or combinations thereof. Each of the conductive routing structures  136  may have substantially the same material composition, or at least one of the conductive routing structures  136  may have a different material composition than at least one other of the conductive routing structures  136 . 
     The conductive contact structures  134 , the conductive routing structures  136 , and the string driver devices  138  may each independently be formed using conventional processes (e.g., conventional deposition processes, conventional photolithography processes, conventional material removal processes) and conventional processing equipment, which are not described in detail herein. 
     Thus, in accordance with embodiments of the disclosure, a method of forming a semiconductor device structure comprises forming a stack structure comprising stacked tiers each comprising an insulating structure and an additional insulating structure longitudinally adjacent the insulating structure. A masking structure is formed over a portion of the stack structure. Portions of the stacked tiers of the stack structure not covered by the masking structure are removed to form at least one staircase structure having steps comprising lateral ends of the stacked tiers. The masking structure is removed after forming the at least one staircase structure. At least one opening is formed laterally inward of the at least one staircase structure, the at least one opening extending through the stacked tiers and continuously across an entire length of the at least one staircase structure. Portions of the additional insulating structure of each of the stacked tiers are replaced with at least one conductive material to form at least one conductive structure in each of the stacked tiers, the at least one conductive structure extending continuously from at least one of the steps of the at least one staircase structure and around the at least one opening to form at least one continuous conductive path extending completely across each of the stacked tiers. 
     In addition, in accordance with additional embodiments of the disclosure, a semiconductor device structure comprises stacked tiers each comprising at least one conductive structure and at least one insulating structure longitudinally adjacent the at least one conductive structure, at least one staircase structure having steps comprising lateral ends of the stacked tiers, and at least one opening extending through the stacked tiers and continuously across an entire length of the at least one staircase structure. The at least one conductive structure of each of the stacked tiers extends continuously from at least one of the steps of the at least one staircase structure and around the at least one opening to form at least one continuous conductive path extending completely across each of the stacked tiers. 
     One of ordinary skill in the art will appreciate that, in accordance with additional embodiments of the disclosure, the features and feature configurations described above in relation to  FIGS.  1 A- 1 G  may be readily adapted to the design needs of different semiconductor devices (e.g., different memory devices, such as different 3D NAND Flash memory devices). By way of non-limiting example,  FIG.  2    illustrates a semiconductor device structure  200  in accordance with another embodiment of the disclosure. The semiconductor device structure  200  may have similar features and functionalities to the semiconductor device structure  100  previously described. However, the semiconductor device structure  200  may, for example, include a relatively greater number of tiers  208 , as well one or more additional features (e.g., additional openings, additional staircase structures, additional conductive contact structures, additional conductive routing structures) and/or feature configurations (e.g., sizes, shapes, arrangements) to account for the relatively greater number of tiers  208 . To avoid repetition, not all features shown in  FIG.  2    are described in detail herein. Rather, unless described otherwise below, features designated by a reference numeral that is a 100 increment of the reference numeral of a feature described previously in relation to one or more of  FIGS.  1 A- 1 G  will be understood to be substantially similar to the feature described previously. 
     As shown in  FIG.  2   , the semiconductor device structure  200  may include a conductive stack structure  224  exhibiting alternating insulating structures and conductive structures  226  arranged in tiers  208 . For clarity, the insulating structures of each of the tiers  208  are not depicted  FIG.  2   . However, aside from variances in shape and size, the insulating structures of the conductive stack structure  224  may be substantially similar to, and may be formed and arranged in substantially the same manner as, the insulating structures  104  previously described in relation to the conductive stack structure  124 . The conductive stack structure  224  may include a greater number of tiers  208  than the number of the tiers  108  included in the conductive stack structure  124  of the semiconductor device structure  100  previously described in relation to  FIGS.  1 F and  1 G . For example, as shown in  FIG.  2   , the conductive stack structure  224  may include twenty-one (21) tiers  208 . In additional embodiments, the conductive stack structure  224  may include a different number of the tiers  208 , such as greater than twenty-one (21) tiers  208  or less than twenty-one (21) tiers  208 . 
     The conductive stack structure  224  may include staircase structures  214 , and openings  220  positioned laterally inward (e.g., in the Y-direction) of the staircase structures  214 . In  FIG.  2   , for clarity in identifying the positions and dimensions of the openings  220 , each of the openings  220  is depicted as being filled with a structure. However, the openings  220  may be substantially free of such structures (e.g., the structures may be absent from the openings  220 ). Alternatively, one or more of the openings  220  may comprise filled openings including the depicted structures therein. The structures may, for example, comprise insulating structures formed of and including at least one insulating material (e.g., an oxide material, such as silicon dioxide, phosphosilicate glass, borosilicate glass, borophosphosilicate glass, fluorosilicate glass, titanium dioxide, zirconium dioxide, hafnium dioxide, tantalum oxide, magnesium oxide, aluminum oxide, or combinations thereof; a nitride material, such as silicon nitride; an oxynitride material, such as silicon oxynitride; amorphous carbon). 
     As shown in  FIG.  2   , the conductive stack structure  224  includes multiple (e.g., more than one) staircase structures  214 . The conductive stack structure  224  may, for example, include multiple stadium structures  218  each including opposing staircase structures  214 . The multiple stadium structures  218  may be positioned in series and in parallel with one another. By way of non-limiting example, as shown in  FIG.  2   , the conductive stack structure  224  may include a first stadium structure  218   a , a second stadium structure  218   b , a third stadium structure  218   c , and a fourth stadium structure  218   d . The first stadium structure  218   a  may include a first forward staircase structure  214   a , and a first reverse staircase structure  214   b  that mirrors the first forward staircase structure  214   a . The second stadium structure  218   b  may extend parallel (e.g., in the X-direction) to the first stadium structure  218   a , and may include a second forward staircase structure  214   c , and a second reverse staircase structure  214   d  that mirrors the second forward staircase structure  214   c . The third stadium structure  218   c  may extend in series (e.g., in the X-direction) to the first stadium structure  218   a , and may include a third forward staircase structure  214   e , and a third reverse staircase structure  214   f  that mirrors the third forward staircase structure  214   e . The fourth stadium structure  218   d  may extend in parallel (in the X-direction) with the third stadium structure  218   c  and in series (e.g., in the X-direction) to the second stadium structure  218   b , and may include a fourth forward staircase structure  214   g , and a fourth reverse staircase structure  214   h  that mirrors the fourth forward staircase structure  214   g . The first stadium structure  218   a  and the second stadium structure  218   b  may be at least partially defined by ends of an upper group  209   a  of the tiers  208  (e.g., tiers  208  positioned relatively higher in the Z-direction), and may serve as redundant and/or alternative means of connecting to the tiers  208  of the upper group  209   a . The third stadium structure  218   c  and the fourth stadium structure  218   d  may be at least partially defined by ends of a lower group  209   b  of the tiers  208  (e.g., tiers  208  positioned relatively lower in the Z-direction), and may serve as redundant and/or alternative means of connecting to the tiers  208  of the lower group  209   b.    
     In additional embodiments, the conductive stack structure  224  may exhibit one or more of a different number and different configuration of the staircase structures  214 . By way of non-limiting example, the conductive stack structure  224  may include only one (1) stadium structure  218  (e.g., only the first stadium structure  218   a , or only the second stadium structure  218   b ) associated with (e.g., at least partially defined by ends of) the upper group  209   a  of the tiers  208 , may include only one (1) stadium structure  218  (e.g., only the third stadium structure  218   c , or only the fourth stadium structure  218   d ) associated with the lower group  209   b  of the tiers  208 , may include more than two (2) stadium structures  218  in parallel with one another and associated with the upper group  209   a  of the tiers  208 , may include more than two (2) stadium structures  218  in parallel with one another and associated with the lower group  209   b  of the tiers  208 , may include additional stadium structures  218  in series with the first stadium structure  218   a  and the third stadium structure  218   c , may include additional stadium structures  218  in series with the second stadium structure  218   b  and the fourth stadium structure  218   d , may include one or more forward staircase structures (e.g., one or more of the first forward staircase structure  214   a , the second forward staircase structure  214   c , the third forward staircase structure  214   e , and the fourth forward staircase structure  214   g ) but not one or more reverse staircase structures (e.g., one or more of the first reverse staircase structure  214   b , the second reverse staircase structure  214   d , the third reverse staircase structure  214   f , and the fourth reverse staircase structure  214   h  may be omitted), and/or may include one or more reverse staircase structures (e.g., one or more of the first reverse staircase structure  214   b , the second reverse staircase structure  214   d , the third reverse staircase structure  214   f , and the fourth reverse staircase structure  214   h ) but not one or more forward staircase structures (e.g., one or more of the first forward staircase structure  214   a , the second forward staircase structure  214   c , the third forward staircase structure  214   e , and the fourth forward staircase structure  214   g  may be omitted). 
     As shown in  FIG.  2   , the openings  220  may longitudinally extend (e.g., in the Z-direction) through the conductive stack structure  224 , may be positioned laterally inward (e.g., in the Y-direction) of the staircase structures  214 , and may continuously laterally extend (e.g., in the X-direction) across entire lengths of the staircase structures  214 . By way of non-limiting example, as shown in  FIG.  2   , the openings  220  may extend completely through each of the tiers  208 , may be positioned laterally inwardly adjacent the stadium structures  218 , and may continuously laterally extend across entire lengths of the stadium structures  218 . A first opening  220   a  may be positioned laterally between (e.g., in the Y-direction) the first stadium structure  218   a  and a middle section  222  of the conductive stack structure  224 , and may laterally extend (e.g., in the X-direction) from a top of the first forward staircase structure  214   a  to a top of the first reverse staircase structure  214   b . A second opening  220   b  may be positioned laterally between (e.g., in the Y-direction) the second stadium structure  218   b  and the middle section  222  of the conductive stack structure  224 , and may laterally extend parallel (e.g., in the X-direction) to the first opening  220   a  from a top of the second forward staircase structure  214   c  to a top of the second reverse staircase structure  214   d . A third opening  220   c  may be positioned laterally between (e.g., in the Y-direction) the third stadium structure  218   c  and the middle section  222  of the conductive stack structure  224 , and may laterally extend (e.g., in the X-direction) from a top of the third forward staircase structure  214   e  to a top of the third reverse staircase structure  214   f . A fourth opening  220   d  may be positioned laterally between (e.g., in the Y-direction) the fourth stadium structure  218   d  and the middle section  222  of the conductive stack structure  224 , and may laterally extend parallel (e.g., in the X-direction) to the third opening  220   c  from a top of the fourth forward staircase structure  214   g  to a top of the fourth reverse staircase structure  214   h.    
     In additional embodiments, the conductive stack structure  224  may include a different number of the openings  220 . By way of non-limiting example, at least one additional opening may be formed in the middle section  222  of the conductive stack structure  224 . The at least one additional opening may, for example, comprise a fifth opening positioned laterally between the first opening  220   a  and the second opening  220   b  and having substantially the same length as the first opening  220   a  and the second opening  220   b , and/or may comprise a sixth opening positioned laterally between the third opening  220   c  and the fourth opening  220   d  and having substantially the same length as the third opening  220   c  and the fourth opening  220   d . The at least one additional opening may extend completely longitudinally through the middle section  222  of the conductive stack structure  224 , and may continuously laterally extend across the middle section  222  in parallel to the other openings  220 . 
     As shown in  FIG.  2   , the conductive structures  226  may follow (e.g., route along) lateral (e.g., side) surfaces of the conductive stack structure  224 . For example, the conductive structures  226  may extend into and along outer lateral surfaces (e.g., peripheral lateral surfaces) of the tiers  208 , as well as into and along inner lateral surfaces of the tiers  208  (e.g., lateral surfaces at least partially defined by the openings  220  longitudinally extending through the tiers  208 ). For each of the tiers  208 , the conductive structures  226  may laterally extend to and around each of the openings  220  (e.g., completely around ends of the openings  220 , and completely across the portions of the middle section  222  of the conductive stack structure  224  adjacent the openings  220 ) to form one or more continuous conductive paths between a first end  230  of the conductive stack structure  224  and a second, opposing end  232  of the conductive stack structure  224 . The first end  230  and the second, opposing end  232  of the conductive stack structure  224  may each be coupled to other components of a semiconductor device (e.g., a memory device) including the semiconductor device structure  200 , such as one or more memory cell arrays (e.g., vertical memory cell arrays). In addition, portions of at least some of the conductive structures  226  may laterally extend (e.g., in the X-direction) to and at least partially define the staircase structures  214  of the conductive stack structure  224  to form conductive contact regions (e.g., landing pad regions) for at least some of the tiers  208 . For example, portions of at least some of the conductive structures  226  of the upper group  209   a  of the tiers  208  may extend to at least partially define the first stadium structure  218   a  and the second stadium structure  218   b , and portions of at least some of the conductive structures  226  of the lower group  209   b  of the tiers  208  may extend to at least partially define the third stadium structure  218   c  and the fourth stadium structure  218   d . For each of the conductive structures  226 , portions thereof laterally extending to and at least partially defining one or more of the staircase structures  214  may be integral and continuous with other portions thereof laterally extending to and around the openings  220  positioned laterally inward of (e.g., laterally adjacent) the staircase structures  214 . Each of the tiers  208  may include multiple (e.g., more than one) conductive structures  226 , or may include a single (e.g., only one) conductive structure  226 . 
     With continued reference to  FIG.  2   , conductive contact structures  234  (e.g., conductive plugs, conductive vertical interconnects) may be coupled (e.g., attached, connected) to the conductive structures  226  of the tiers  208  at one or more of the staircase structures  214 , and conductive routing structures  236  (e.g., conductive interconnects, conductive bridges) may be coupled to the conductive contact structures  234  and to one or more string driver devices  238 . The string driver devices  238  may be formed of and include a plurality of switching devices (e.g., transistors). Suitable designs and configurations for the string driver devices  238  are well known in the art, and are therefore not described in detail herein. The string driver devices  238  may, for example, underlie one or more portions (e.g., central portions, peripheral portions, combinations thereof) of the conductive stack structure  224 . 
     The conductive contact structures  234  and the conductive routing structures  236  may electrically connect the conductive structures  226  of the tiers  208  to the string driver devices  238 . By way of non-limiting example, as shown in  FIG.  2   , a portion of the conductive contact structures  234  and the conductive routing structures  236  may electrically connect the upper group  209   a  of the tiers  208  to one or more of the string driver devices  238  at one or more of the staircase structures  214 , and another portion of the conductive contact structures  234  and the conductive routing structures  236  may electrically connect the lower group  209   b  of the tiers  208  to one or more of the string driver devices  238  at one or more other of the staircase structures  214 . A portion of the conductive contact structures  234  and the conductive routing structures  236  may be coupled to and extend between at least one of the string driver devices  238  and steps  216  of one or more of the first stadium structure  218   a  (e.g., steps  216  of the first forward staircase structure  214   a , and/or steps  216  of the first reverse staircase structure  214   b ) and the second stadium structure  218   b  (e.g., steps  216  of the second forward staircase structure  214   c  and/or steps  216  of the second reverse staircase structure  214   d ) to electrically connect the conductive structures  226  of at least some of the upper group  209   a  of the tiers  208  to the string driver device  238 . In addition, another portion of the conductive contact structures  234  and the conductive routing structures  236  may be coupled to and extend between at least one string driver device  238  and steps  216  of one or more of the third stadium structure  218   c  (e.g., steps  216  of the third forward staircase structure  214   e , and/or steps  216  of the third reverse staircase structure  214   f ) and the fourth stadium structure  218   d  (e.g., steps  216  of the fourth forward staircase structure  214   g , and/or steps  216  of the fourth reverse staircase structure  214   h ) to electrically connect the conductive structures  226  of at least some of the lower group  209   b  of the tiers  208  to the string driver device  238 . The continuous conductive paths across the conductive stack structure  224  (e.g., from the first end  230  to the second, opposing end  232 ) provided by the configurations of the conductive structures  226  may permit an individual (e.g., single) switching device (e.g., transistor) of the string driver device  238  to drive voltages completely across (e.g., from the first end  230  to the second, opposing end  232 ) and/or in opposing directions across (e.g., toward the first end  230  and toward the second, opposing end  232 ) an individual tier  208  electrically connected thereto. 
       FIGS.  3 A through  3 F  are simplified perspective ( FIGS.  3 A through  3 E ) and top-down ( FIG.  3 F ) views illustrating embodiments of a method of forming another semiconductor device structure including a staircase structure, such as a memory array structure (e.g., a memory array block) for a 3D non-volatile memory device (e.g., a 3D NAND Flash memory device). With the description provided below, it will be readily apparent to one of ordinary skill in the art that the methods described herein may be used in various devices. In other words, the methods of the disclosure may be used whenever it is desired to form a semiconductor device including a staircase structure. 
     Referring to  FIG.  3 A , a semiconductor device structure  300  may include a stack structure  302  exhibiting an alternating sequence of insulating structures  304  and additional insulating structures  306  arranged in tiers  308 . Each of the tiers  308  may include one of the insulating structures  304  and one of the additional insulating structures  306 . The stack structure  302 , including the tiers  308  of the insulating structures  304  and the additional insulating structures  306 , may be substantially similar to and may be formed in substantially the same manner as the stack structure  102  previously described herein with reference to  FIG.  1 A . As shown in  FIG.  3 A , in some embodiments, the alternating sequence of the insulating structures  304  and the additional insulating structures  306  begins with one of the insulating structures  304 . In additional embodiments, the arrangement of the insulating structures  304  and the additional insulating structures  306  is switched relative to that depicted in  FIG.  3 A  (e.g., the alternating sequence of the insulating structures  304  and the additional insulating structures  306  begins with one of the additional insulating structures  306 ). 
     Referring to next to  FIG.  3 B , portions of the stack structure  302  ( FIG.  3 A ) (e.g., portions of one or more of the tiers  308 ) may be subjected to at least one material removal process (e.g., one or more of a trimming process and a chopping process) to form a modified stack structure  310 . The modified stack structure  310  may include one or more staircase structures  312  each independently formed of and including one or more steps  314 . The steps  314  of the one or more staircase structures  312  may be at least partially defined by exposed portions of one or more of the tiers  308  remaining following the at least one material removal process. 
     The modified stack structure  310  may include a single (e.g., only one) staircase structure  312 , or may include multiple (e.g., more than one) staircase structures  312 . In some embodiments, the modified stack structure  310  includes multiple staircase structures  312 . By way of non-limiting example, as shown in  FIG.  3 B , the modified stack structure  310  may include a stadium structure  316  including a forward staircase structure  312   a , and a reverse staircase structure  312   b  that mirrors the forward staircase structure  312   a . In additional embodiments, the modified stack structure  310  may exhibit one or more of a different number and different configuration of staircase structures  312 . By way of non-limiting example, the modified stack structure  310  may include two or more stadium structures  316  in series with one another, may include one or more forward staircase structures (e.g., the forward staircase structure  312   a ) but not one or more reverse staircase structures (e.g., the reverse staircase structure  312   b  may be omitted), may include one or more reverse staircase structures (e.g., reverse staircase structure  312   b ) but not one or more forward staircase structures (e.g., the forward staircase structure  312   a  may be omitted), may include two or more forward staircase structures in series with one another, and/or may include two or more reverse staircase structures in series with one another. 
     Each of the staircase structures  312  included in the modified stack structure  310  may independently include a desired number of steps  314 . The number of steps  314  included in each of the staircase structures  312  may be substantially the same as (e.g., equal to) or may be different than (e.g., less than, or greater than) the number of tiers  308  in the modified stack structure  310 . In some embodiments, the number of steps  314  included in each of the staircase structures  312  is less than the number of tiers  308  in the modified stack structure  310 . As a non-limiting example, as shown in  FIG.  3 B , each of the staircase structures  312  (e.g., the forward staircase structure  312   a  and the reverse staircase structure  312   b ) may include ten (10) steps  314  at least partially defined by ends of the eleven (11) tiers  308  (e.g., tiers  308   a  through  308   k ) of the modified stack structure  310 . In additional embodiments, one or more of the staircase structures  312  may include a different number of steps  314  (e.g., less than ten (10) steps, greater than ten (10) steps). As a non-limiting example, if the modified stack structure  310  includes eleven (11) tiers  308 , at least one of the staircase structures  312  may include five (5) steps  314  at least partially defined by ends of a relatively lower group of the tiers  308  (e.g., tier  308   f  through tier  308   k ), and at least one other of the staircase structures  312  may include five (5) steps  314  at least partially defined by ends of a relatively higher group of the tiers  308  (e.g., tiers  308   a  through  308   e ). 
     The dimensions of each of the steps  314  may independently be tailored to desired dimensions and positions of additional structures (e.g., conductive structures, conductive contact structures) and/or openings (e.g., slots) to be formed in, on, over, and/or adjacent to the steps  314  during subsequent processing of the semiconductor device structure  300 , as described in further detail below. As shown in  FIG.  3 B , each of the steps  314  may exhibit substantially the same width W 3  as the modified stack structure  310 . In addition, each of the steps  314  may exhibit substantially the same length, or at least one of the steps  314  may exhibit a different length than at least one other of the steps  314 . 
     The staircase structures  312  may be formed using conventional processes (e.g., conventional photolithography processes, conventional material removal processes) and conventional processing equipment, which are not described in detail herein. By way of non-limiting example, a photoresist structure may be formed on or over the stack structure  302  ( FIG.  3 A ), the photoresist structure may be photolithographically processed (e.g., photoexposed and developed) to remove at least one width thereof, one or more of the tiers  308  may be etched (e.g., anisotropically etched, such as anisotropically dry etched) using the remaining portions of the photoresist structure as an etching mask, the photoresist structure may be subjected to additional photolithographic processing to remove at least one additional width thereof, at least another group of the tiers  308  (e.g., the previously etched tier(s)  308  and one or more additional tier(s)  308 ) may be etched using the new remaining portions of the photoresist structure as etching masks, and so on, until the modified stack structure  310  including the one or more staircase structures  312  is formed. 
     Referring next to  FIG.  3 C , one or more openings  318  (e.g., slots, apertures, slits) may be formed in the modified stack structure  310 . The openings  318  may extend through (e.g., completely through) the modified stack structure  310 , and may divide (e.g., segment) the staircase structures  312  ( FIG.  3 B ) into additional staircase structures  320  exhibiting relatively smaller widths than the staircase structures  312 . The one or more openings  318  may laterally intervene (e.g., in the Y-direction) between the additional staircase structures  320  and may continuously laterally extend (e.g., in the X-direction) across the entire lengths of the additional staircase structures  320 . 
     Any desired number (e.g., quantity, amount) of openings  318  may be formed in the modified stack structure  310 . The number of openings  318  may correspond to desired numbers and configurations (e.g., shapes, sizes, positions) of the additional staircase structures  320 . A single (e.g., only one) opening  318  may be formed longitudinally through (e.g., in the Z-direction) and may extend continuously laterally across and between (e.g., in the X-direction) the staircase structures  312  ( FIG.  3 B ) (e.g., the forward staircase structure  312   a  and the reverse staircase structure  312   b  of the stadium structure  316 ) of the modified stack structure  310 , or multiple (e.g., more than one) openings  318  may be formed longitudinally through and may extend continuously laterally in parallel across and between the staircase structures  312  of the modified stack structure  310 . As shown in  FIG.  3 C , in some embodiments, three (3) openings  318  are formed in the modified stack structure  310 . The three (3) openings  318  may at least partially define and separate (e.g., in the Y-direction) four (4) additional stadium structures  322 . A first opening  318   a  may be laterally disposed between a first additional stadium structure  322   a  and a second additional stadium structure  322   b , a second opening  318   b  may be laterally disposed between the second additional stadium structure  322   b  and a third additional stadium structure  322   c , and a third opening  318   c  may be laterally disposed between the third additional stadium structure  322   c  and a fourth additional stadium structure  322   d . The first additional stadium structure  322   a  may include a first forward staircase structure  320   a  and a first reverse staircase structure  320   b . The second additional stadium structure  322   b  may include a second forward staircase structure  320   c  and a second reverse staircase structure  320   d . The third additional stadium structure  322   c  may include a third forward staircase structure  320   e  and a third reverse staircase structure  320   f . The fourth additional stadium structure  322   d  may include a fourth forward staircase structure  320   g  and a fourth reverse staircase structure  320   h . In additional embodiments, a different number of openings  318  (e.g., less than three (3) openings  318 , or more than three (3) openings  318 ) may be formed longitudinally through and continuously laterally across and between the staircase structures  312  ( FIG.  3 B ). By way of non-limiting example, two (2) openings  318  may be formed in the modified stack structure  310  to at least partially define and separate three (3) additional stadium structures  322 , or one (1) opening  318  may be formed in the modified stack structure  310  to at least partially define and separate two (2) additional stadium structures  322 . 
     The dimensions and spacing of the one or more openings  318  may be selected to provide desired dimensions (e.g., widths) to the additional staircase structures  320  (including steps  324  thereof), and to provide desired dimensions (e.g., widths) and spacing to conductive structures to be formed using the openings  318 , as described in further detail below. If more than one opening  318  is formed in the modified stack structure  310 , each of the openings  318  may exhibit substantially the same dimensions (e.g., substantially the same width, length, and height), or at least one of the openings  318  may exhibit one or more different dimensions (e.g., a different width, a different length, and/or a different height) than at least one other of the openings  318 . In some embodiments, each of the openings  318  exhibits substantially the same dimensions. In addition, if more than two (2) openings  318  are formed in the modified stack structure  310 , adjacent openings  318  may be substantially uniformly (e.g., evenly) spaced apart from one another, or may be non-uniformly (non-evenly) spaced apart from one another. In some embodiments, adjacent openings  318  are substantially uniformly spaced apart from one another. The openings  318  may be symmetrically distributed across the modified stack structure  310 , or may be asymmetrically distributed across the modified stack structure  310 . 
     The openings  318  may be formed in the modified stack structure  310  using one or more conventional material removal processes, which are not described in detail herein. For example, one or more portions of the modified stack structure  310  may be subjected to at least one etching process (e.g., at least one dry etching process, such as at least one of an RIE process, a deep RIE process, a plasma etching process, a reactive ion beam etching process, and a chemically assisted ion beam etching process; at least one wet etching process, such as at least one of a hydrofluoric acid etching process, a buffered hydrofluoric acid etching process, and a buffered oxide etching process) to form the openings  318  in the modified stack structure  310 . 
     Referring to  FIG.  3 D , portions of the additional insulating structures  306  ( FIG.  3 C ) may be selectively removed, and may be replaced with conductive material to form a conductive stack structure  326 . As shown in  FIG.  3 D , each of the tiers  308  of the conductive stack structure  326  may include one or more conductive structures  328  (e.g., conductive gates, conductive plates) extending (e.g., in the X-direction and/or the Y-direction) into lateral surfaces thereof. The one or more conductive structures  328  of each tier  308  of the conductive stack structure  326  may at least partially (e.g., substantially) laterally surround remaining portions  330  (e.g., unremoved portions) of the additional insulating structures  306 . 
     The conductive structures  328  may follow (e.g., route along) lateral (e.g., side) surfaces of the conductive stack structure  326 . For example, the conductive structures  328  may extend into and along outer lateral surfaces (e.g., peripheral lateral surfaces) of the tiers  308 , as well as into and along inner lateral surfaces of the tiers  308  (e.g., lateral surfaces at least partially defined by the openings  318  longitudinally extending through the tiers  308 ). Portions of at least some of the conductive structures  328  may laterally extend (e.g., in the X-direction) to and at least partially define the additional staircase structures  320  of the conductive stack structure  326  to form conductive contact regions (e.g., landing pad regions) for at least some of the tiers  308 . In addition, in tiers  308  longitudinally below the additional staircase structures  320  (e.g., untrimmed tiers  308  and/or unchopped tiers  308 ), the conductive structures  328  thereof may laterally extend to and may completely surround the openings  318  to form one or more continuous conductive paths between a first end  332  of the conductive stack structure  326  and a second, opposing end  334  of the conductive stack structure  326 . The first end  332  and the second, opposing end  334  of the conductive stack structure  326  may each be coupled to other components of a semiconductor device (e.g., a memory device) including the semiconductor device structure  300 , such as one or more memory cell arrays (e.g., vertical memory cell arrays). 
     As shown in  FIG.  3 D , the conductive stack structure  326  may include multiple (e.g., more than one) conductive structures  328  in each of the tiers  308  defining the additional staircase structures  320 . For example, for each of the tiers  308  defining the additional stadium structures  322 , at least one conductive structure  328  may at least partially define the steps  324  of each of the forward staircase structures (e.g., each of the first forward staircase structure  320   a , the second forward staircase structure  320   c , the third forward staircase structure  320   e , and the fourth forward staircase structure  320   g ), and at least one other conductive structure  328  may at least partially define the steps  324  of each of the reverse staircase structures (e.g., each of the first reverse staircase structure  320   b , the second reverse staircase structure  320   d , the third reverse staircase structure  320   f , and the fourth reverse staircase structure  320   h ). The conductive structure  328  at least partially defining the steps  324  of each of the forward staircase structures may extend laterally inward from the first end  332  of the conductive stack structure  326 , and may partially surround sides of each of the openings  318  (e.g., the first opening  318   a , the second opening  318   b , and the third opening  318   c ). The other conductive structure  328  at least partially defining the steps  324  of each of the reverse staircase structures may extend laterally inward from the second, opposing end  334  of the conductive stack structure  326 , and may also partially surround sides of each of the openings  318 . In some embodiments, for each of the tiers  308  defining the additional staircase structures  320 , a single (e.g., only one) conductive structure  328  extends laterally inward from the first end  332  of the conductive stack structure  326 , and a single (e.g., only one) other conductive structure  328  extends laterally inward from the second, opposing end  334  of the conductive stack structure  326 . In additional embodiments, for one or more of the tiers  308  defining the additional staircase structures  320 , multiple (e.g., more than one) conductive structures  328  extend laterally inward from the first end  332  of the conductive stack structure  326 , and/or multiple other conductive structures  328  extend laterally inward from the second, opposing end  334  of the conductive stack structure  326 . By way of non-limiting example, in some embodiments wherein the second opening  318   b  is omitted (e.g., absent), one or more of the tiers  308  may individually include at least two (2) of the conductive structures  328  extending laterally inward from the first end  332 , and/or at least two (2) of the conductive structures  328  extending laterally inward from the second, opposing end  334 . In such embodiments, the at least two (2) of the conductive structures  328  extending laterally inward from the first end  332  may be separated (e.g., isolated) from one another by a remaining portion of one of the additional insulating structures  306  ( FIG.  3 C ), and/or the at least two (2) of the conductive structures  328  extending laterally inward from the second, opposing end  334  may be separated (e.g., isolated) from one another by a remaining portion of one of the additional insulating structures  306  ( FIG.  3 C ). 
     For tiers  308  (e.g., untrimmed tiers  308  and/or unchopped tiers  308 ) longitudinally below those defining the additional staircase structures  320 , each tier  308  may include a single (e.g., only one) conductive structure  328 , or one or more tiers  308  may individually include multiple (e.g., more than one) conductive structures  328 . In some embodiments, each of the tiers  308  longitudinally below those defining the additional staircase structures  320  includes a single conductive structure  328 . The single conductive structure  328  may extend laterally inward from the first end  332  and the second, opposing end  334  of the conductive stack structure  326  along outer lateral surfaces of the conductive stack structure  326 , and may substantially completely surround each of the openings  318  (e.g., each of the first opening  318   a , the second opening  318   b , and the third opening  318   c ) to form a continuous conductive path extending from the first end  332  of the conductive stack structure  326  to the second, opposing end  334  of the of the conductive stack structure  326 . In additional embodiments, one or more of the tiers  308  longitudinally below those defining the additional staircase structures  320  individually include multiple conductive structures  328 . By way of non-limiting example, in some embodiments wherein the second opening  318   b  is omitted (e.g., absent), one or more of the tiers  308  longitudinally below those defining the additional staircase structures  320  may individually include at least two (2) conductive structures  328  extending laterally inward from the first end  332  and the second, opposing end  334  of the conductive stack structure  326 . In such embodiments, the at least two (2) conductive structures  328  may be separated (e.g., isolated) from one another by a remaining portion of one of the additional insulating structures  306  ( FIG.  3 C ). 
     The dimensions and shapes of the conductive structures  328  may directly correspond to the dimensions and shapes of the removed portions of the additional insulating structures  306  ( FIG.  3 C ). A width (e.g., lateral depth within the conductive stack structure  326 ) of each of the conductive structures  328  may be substantially uniform across the entire path (e.g., route) of the conductive structure  328 , or the width of at least one of the conductive structures  328  may be substantially non-uniform (e.g., variable) across different portions of the path of the conductive structure  328 . In some embodiments, portions of the conductive structures  328  laterally extending (e.g., in the X-direction) to and at least partially defining the additional staircase structures  320  may exhibit substantially the same width as other portions (e.g., insulating structure  304  portions) of the additional staircase structures  320 . In addition, each of the conductive structures  328  may exhibit a different shape and at least one different dimension than each other of the conductive structures  328 , or at least one of the conductive structures  328  may exhibit one or more of substantially the same shape and substantially the same dimensions as at least one other of the conductive structures  328 . By way of non-limiting example, as shown in  FIG.  3 D , conductive structures  328  of different tiers  308  may exhibit different shapes and different dimensions (e.g., different lengths associated with the locations of the different steps  324  of the additional staircase structures  320 ) than one another, but conductive structures  328  within the same tier  308  may exhibit substantially the same shapes and substantially the same dimensions as one another (e.g., conductive structures  328  within the same tier  308  may be mirror images of one another). In additional embodiments, conductive structures  328  of two or more different tiers  308  may exhibit substantially the same shapes and substantially the same dimensions as one another. In further embodiments, conductive structures  328  within the same tier  308  may exhibit one or more of a different shape and at least one different dimension than one another. 
     The conductive structures  328  may be formed of and include at least one conductive material, such as a metal, a metal alloy, a conductive metal oxide, a conductive metal nitride, a conductive metal silicide, a conductively-doped semiconductor material, or combinations thereof. By way of non-limiting example, the conductive structures  328  may be formed of and include at least one of tungsten W, WN, Ni, Ta, TaN, TaSi, Pt, Cu, Ag, Au, Al, Mo, Ti, TiN, TiSi, TiSiN, TiAlN, MoN, Ir, IrOx, Ru, RuO x , and conductively-doped silicon. In some embodiments, the conductive structures  328  are formed of and include W. 
     The conductive structures  328  may be formed by selectively removing portions of the additional insulating structures  306  ( FIG.  3 C ) relative to the insulating structures  304  to form recessed regions laterally extending into each of the tiers  308 , and then at least partially (e.g., substantially) filling the recessed regions with at least one conductive material. The recessed regions may be formed by subjecting the modified stack structure  310  ( FIG.  3 C ) to at least one etching processing (e.g., an isotropic etching process) employing an etch chemistry in which the insulative material of the additional insulating structures  306  is selectively removed relative to that of the insulating structures  304 . By way of non-limiting example, if the insulating structures  304  are formed of and include silicon dioxide (SiO 2 ), and the additional insulating structures  306  are formed of and include silicon nitride (Si 3 N 4 ), the modified stack structure  310  may be exposed to an etchant comprising phosphoric acid (H 3 O 4 P) to selectively remove portions of the additional insulating structures  306  adjacent exposed lateral surfaces (e.g., exposed outer lateral surfaces, exposed inner lateral surfaces at least partially defined by the openings  318 ) of the modified stack structure  310 . Thereafter, the conductive material may be formed (e.g., delivered, deposited) within recessed regions to form the conductive structures  328 . 
     In additional embodiments, rather than selectively removing and replacing portions of the additional insulating structures  306  ( FIG.  3 C ) to form the conductive stack structure  326 , portions of the insulating structures  304  may instead be selectively removed and replaced with a conductive material to form a conductive stack structure. Aside from the sequence (e.g., order) of the alternating conductive structures and insulating structures of such a conductive stack structure and differences (if any) associated with material properties of the insulating structures  304  as compared to those of the additional insulating structures  306 , such a conductive stack structure may be substantially similar to and may have little or no difference in terms of functionality and/or operability as compared to the conductive stack structure  326  depicted in  FIG.  3 D . 
     Referring next to  FIG.  3 E , conductive contact structures  336  (e.g., conductive plugs, conductive vertical interconnects) may be formed on, over, and/or within the one or more of the additional staircase structures  320  of the conductive stack structure  326 , conductive routing structures  338  (e.g., conductive interconnects, conductive bridges) may be formed on and between some of the conductive contact structures  336  to electrically connect separate (e.g., discrete, isolated) conductive structures  328  of one or more of the tiers  308 , and additional conductive routing structures  340  may be formed on and between other of the conductive contact structures  336  and at least one string driver device  342  to electrically connect the conductive structures  328  of one or more of the tiers  308  to the string driver device  342 .  FIG.  3 F  is a top-down view of the semiconductor device structure  300  at the processing stage depicted in  FIG.  3 E . 
     The conductive contact structures  336  may be coupled to the conductive structures  328  of the tiers  308  of the conductive stack structure  326  at the steps  324  of the additional staircase structures  320 . Each of the tiers  308  (e.g., each of the tiers  308   a  through  308   k ) may have one or more of the conductive contact structures  336  coupled to the conductive structures  328  thereof, or less than all of the tiers  308  (e.g., less than all of the tiers  308   a  through  308   k , such as only tiers  308   b  through  308   j ) may have one or more of the conductive contact structures  336  coupled to the conductive structures  328  thereof. 
     As shown in  FIG.  3 E , each of the tiers  308  having conductive contact structures  336  coupled thereto may include at least two (2) first conductive contact structures  336   a  positioned to electrically connect (with the use of at least one of the conductive routing structures  338 ) separate conductive structures  328  of the tier  308 . For example, for each of the tiers  308  defining the additional stadium structures  322 , at least one first conductive contact structure  336   a  may be coupled to at least one conductive structure  328  of the tier  308  at a step  324  of at least one forward staircase structure (e.g., one or more of the first forward staircase structure  320   a , the second forward staircase structure  320   c , the third forward staircase structure  320   e , and the fourth forward staircase structure  320   g ), and at least one additional first conductive contact structure  336   a  may be coupled to at least one other conductive structure  328  of the tier  308  at a step  324  of at least one reverse staircase structure (e.g., one or more of the first reverse staircase structure  320   b , the second reverse staircase structure  320   d , the third reverse staircase structure  320   f , and the fourth reverse staircase structure  320   h ). By way of non-limiting example, as depicted in  FIG.  3 E , for each of the tiers  308  defining the additional stadium structures  322 , a first conductive contact structure  336   a  may be coupled to a first conductive structure  328  of the tier  308  at a step  324  of the fourth forward staircase structure  320   g  of the fourth additional stadium structure  322   d , and another first conductive contact structure  336   a  may be coupled to a second conductive structure  328  of the tier  308  at a step  324  of the fourth reverse staircase structure  320   h  of the fourth additional stadium structure  322   d.    
     In addition, as shown in  FIG.  3 E , each of the tiers  308  having conductive contact structures  336  coupled thereto may include one or more second conductive contact structures  336   b  positioned to electrically connect (with the use of at least one of the additional conductive routing structures  340 ) the conductive structures  328  of the tier  308  to at least one of the string driver devices  342 . For example, for each of the tiers  308  defining the additional stadium structures  322 , at least one second conductive contact structure  336   b  may be coupled to at least one conductive structure  328  of the tier  308  at a step  324  of at least one of the additional staircase structures  320  (e.g., one or more of the first forward staircase structure  320   a , the first reverse staircase structure  320   b , the second forward staircase structure  320   c , the second reverse staircase structure  320   d , the third forward staircase structure  320   e , the third reverse staircase structure  320   f , the fourth forward staircase structure  320   g , and the fourth reverse staircase structure  320   h ). By way of non-limiting example, as depicted in  FIG.  3 E , for each of the tiers  308  defining the additional stadium structures  322 , a second conductive contact structure  336   b  may be coupled to at least one of the conductive structures  328  of the tier  308  at one or more of a step  324  of the first forward staircase structure  320   a  of the first additional stadium structure  322   a  and a step  324  of the first reverse staircase structure  320   b  of the first additional stadium structure  322   a.    
     The second conductive contact structures  336   b  may be formed on or over a single (e.g., only one) additional staircase structure  320  of the conductive stack structure  326 , or may be formed on or over multiple (e.g., more than one) additional staircase structures  320  of the conductive stack structure  326 . By way of non-limiting example, as shown in  FIGS.  3 E and  3 F , within at least one of the additional stadium structures  322  (e.g., one or more of the first additional stadium structure  322   a , the second additional stadium structure  322   b , the third additional stadium structure  322   c , and the fourth additional stadium structure  322   d ) of the conductive stack structure  326 , a portion of the second conductive contact structures  336   b  may be formed on or over a forward staircase structure (e.g., the first forward staircase structure  320   a , the second forward staircase structure  320   c , the third forward staircase structure  320   e , the fourth forward staircase structure  320   g ) and an additional portion of the second conductive contact structures  336   b  may be formed on or over a reverse staircase structure (e.g., the first reverse staircase structure  320   b , the second reverse staircase structure  320   d , the third reverse staircase structure  320   f , the fourth reverse staircase structure  320   h ). In additional embodiments, within at least one of the additional stadium structures  322 , each of the second conductive contact structures  336   b  may be formed on or over a forward staircase structure (e.g., the first forward staircase structure  320   a , the second forward staircase structure  320   c , the third forward staircase structure  320   e , the fourth forward staircase structure  320   g ). In further embodiments, within at least one of the additional stadium structures  322 , each of the second conductive contact structures  336   b  may be formed on or over a reverse staircase structure (e.g., the first reverse staircase structure  320   b , the second reverse staircase structure  320   d , the third reverse staircase structure  320   f , the fourth reverse staircase structure  320   h ). 
     Conductive contact structures  336  (e.g., first conductive contact structures  336   a , second conductive contact structures  336   b ) formed on or over the same additional staircase structure  320  may be substantially uniformly (e.g., evenly) spaced apart from one another, or may be non-uniformly (e.g., unevenly) spaced apart from one another. Conductive contact structures  336  formed on or over the same additional staircase structure  320  may be formed to be generally centrally positioned (e.g., in at least the X-direction) on or over the steps  324  associated therewith. Accordingly, distances between adjacent conductive contact structures  336  located on or over the same additional staircase structure  320  may vary in accordance with variance in the lengths (e.g., in the X-direction) of the adjacent steps  324  associated with the adjacent conductive contact structures  336 . In addition, conductive contact structures  336  formed on or over the same additional staircase structure  320  may be substantially aligned with one another (e.g., not offset from one another in the Y-direction), or may be at least partially non-aligned with one another (e.g., offset from one another in the Y-direction). 
     The conductive contact structures  336  may be formed of and include at least one conductive material, such as a metal (e.g., tungsten, titanium, molybdenum, niobium, vanadium, hafnium, tantalum, chromium, zirconium, iron, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium, platinum, copper, silver, gold, aluminum), a metal alloy (e.g., a cobalt-based alloy, an iron-based alloy, a nickel-based alloy, an iron- and nickel-based alloy, a cobalt- and nickel-based alloy, an iron- and cobalt-based alloy, a cobalt- and nickel- and iron-based alloy, an aluminum-based alloy, a copper-based alloy, a magnesium-based alloy, a titanium-based alloy, a steel, a low-carbon steel, a stainless steel), a conductive metal-containing material (e.g., a conductive metal nitride, a conductive metal silicide, a conductive metal carbide, a conductive metal oxide), a conductively-doped semiconductor material (e.g., conductively-doped silicon, conductively-doped germanium, conductively-doped silicon germanium), or combinations thereof. Each of the conductive contact structures  336  may have substantially the same material composition, or at least one of the conductive contact structures  336  may have a different material composition than at least one other of the conductive contact structures  336 . 
     With continued reference to  FIGS.  3 E and  3 F , the conductive routing structures  338  may be coupled (e.g., attached, connected) to and extend between portions of the conductive contact structures  336  (e.g., portions of the first conductive contact structures  336   a ). The conductive routing structures  338  may form a conductive path between (e.g., electrically connect) electrically isolated conductive structures  328  of one or more of the tiers  308  ( FIG.  3 E ) of the conductive stack structure  326 . For example, for each of the tiers  308  defining the additional stadium structures  322 , the combination of the first conductive contact structures  336   a  and the conductive routing structures  338  may electrically connect at least one conductive structure  328  of the tier  308  located proximate the first end  332  of the conductive stack structure  326  to at least one other conductive structure  328  of the tier  308  located proximate the second, opposing end  334  of the conductive stack structure  326 . 
     The conductive routing structures  338  may extend from a portion of the conductive contact structures  336  (e.g., a portion of the first conductive contact structures  336   a ) located proximate the first end  332  of the conductive stack structure  326 , over one or more sections of the conductive stack structure  326 , and to other portions of the conductive contact structures  336  (e.g., another portion of the first conductive contact structures  336   a ) located proximate the second, opposing end  334  of the conductive stack structure  326 . For example, for each of the tiers  308  defining the additional stadium structures  322 , at least one conductive routing structure  338  extends from at least one first conductive contact structure  336   a  positioned on or over a step  324  of at least one forward staircase structure (e.g., one or more of the first forward staircase structure  320   a , the second forward staircase structure  320   c , the third forward staircase structure  320   e , and the fourth forward staircase structure  320   g ) to at least one other first conductive contact structure  336   a  positioned on or over a step  324  of at least one reverse staircase structure (e.g., one or more of the first reverse staircase structure  320   b , the second reverse staircase structure  320   d , the third reverse staircase structure  320   f , and the fourth reverse staircase structure  320   h ). By way of non-limiting example, as shown in  FIGS.  3 E and  3 F , for each of the tiers  308  defining the additional stadium structures  322 , a conductive routing structure  338  may extend from a first conductive contact structure  336   a  located on or over a step  324  of the fourth forward staircase structure  320   g  of the fourth additional stadium structure  322   d  to another first conductive contact structure  336   a  located on or over a step  324  of the fourth reverse staircase structure  320   h  of the fourth additional stadium structure  322   d.    
     With continued reference to  FIG.  3 E , the additional conductive routing structures  340  may be coupled (e.g., attached, connected) to portions of the conductive contact structures  336  (e.g., portions of the second conductive contact structures  336   b ) and at least one string driver device  342 . The string driver device  342  may be formed of and include a plurality of switching devices (e.g., transistors). Suitable designs and configurations for the string driver device  342  are well known in the art, and are therefore not described in detail herein. The string driver device  342  may, for example, underlie one or more portions (e.g., central portions, peripheral portions, combinations thereof) of the conductive stack structure  326 . The combination of the conductive contact structures  336  (e.g., the first conductive contact structures  336   a  and the second conductive contact structures  336   b ), the conductive routing structures  338 , and the additional conductive routing structures  340  may electrically connect the conductive structures  328  of one or more of the tiers  308  to the string driver device  342 , facilitating application of voltages to the conductive structures  328  using the string driver device  342 . The continuous conductive paths across the conductive stack structure  326  (e.g., from the first end  332  to the second, opposing end  334 ) provided by the configurations and positions of the conductive structures  328 , the conductive contact structures  336  (e.g., the first conductive contact structures  336   a ), and the conductive routing structures  338  may permit an individual (e.g., single) switching device (e.g., transistor) of the string driver device  342  to drive voltages completely across (e.g., from the first end  332  to the second, opposing end  334 ) and/or in opposing directions across (e.g., toward the first end  332  and toward the second, opposing end  334 ) an individual tier  308  electrically connected thereto. 
     The additional conductive routing structures  340  may extend from the conductive contact structures  336  (e.g., the second conductive contact structures  336   b ), over one or more sections of the conductive stack structure  326 , through one or more additional sections of the conductive stack structure  326 , and to one or more of the string driver devices  342 . By way of non-limiting example, as shown in  FIG.  3 E , the additional conductive routing structures  340  may extend from the second conductive contact structures  336   b , laterally over a middle section of the conductive stack structure  326 , longitudinally through insulating sections of the tiers  308  including the remaining portions  330  of the additional insulating structures  306  ( FIG.  3 C ) and portions of the insulating structures  304 , and to the string driver devices  342 . In addition, each of the additional conductive routing structures  340  may extend to the same string driver device  342 , or at least one of the additional conductive routing structures  340  may extend to a different string driver device  342  than at least one other of the additional conductive routing structures  340 . 
     The conductive routing structures  338  and the additional conductive routing structures  340  may be formed of and include at least one conductive material, such as a metal (e.g., W, Ti, Mo, Nb, V, Hf, Ta, Cr, Zr, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Al), a metal alloy (e.g., a Co-based alloy, an Fe-based alloy, a Ni-based alloy, an Fe- and Ni-based alloy, a Co- and Ni-based alloy, an Fe- and Cu-based alloy, a Co- and Ni- and Fe-based alloy, an Al-based alloy, a Cu-based alloy, a Mg-based alloy, a Ti-based alloy, a steel, a low-carbon steel, a stainless steel), a conductive metal-containing material (e.g., a conductive metal nitride, a conductive metal silicide, a conductive metal carbide, a conductive metal oxide), a conductively-doped semiconductor material (e.g., conductively-doped silicon, conductively-doped germanium, conductively-doped silicon germanium), or combinations thereof. Each of the conductive routing structures  338  and each of the additional conductive routing structures  340  may have substantially the same material composition, or one or more of the conductive routing structures  338  and the additional conductive routing structures  340  may have a different material composition than one or more other of the conductive routing structures  338  and the additional conductive routing structures  340 . 
     The conductive contact structures  336 , the conductive routing structures  338 , the additional conductive routing structures  340 , and the string driver devices  342  may each independently be formed using conventional processes (e.g., conventional deposition processes, conventional photolithography processes, conventional material removal processes) and conventional processing equipment, which are not described in detail herein. 
     Thus, in accordance with embodiments of the disclosure, a method of forming a semiconductor device structure comprises forming a stack structure comprising stacked tiers each comprising an insulating structure and an additional insulating structure longitudinally adjacent the insulating structure. Portions of the stacked tiers of the stack structure are removed to form at least one stadium structure comprising opposing staircase structures. At least one opening is formed to extend through the stacked tiers and continuously across an entire length of the at least one stadium structure to form additional stadium structures each comprising additional opposing staircase structures having steps comprising lateral ends of the stacked tiers. Portions of the additional insulating structure of each of the stacked tiers are replaced with at least one conductive material to form conductive structures in each of the stacked tiers. The conductive contact structures are coupled to the conductive structures of the stacked tiers at steps of the additional opposing staircase structures of at least one of the additional stadium structure. Conductive routing structures are coupled to and completely between pairs of the conductive contact structures to form at least one continuous conductive path extending completely across each of the stacked tiers. 
     In addition, in accordance with additional embodiments of the disclosure, a semiconductor device structure comprises stacked tiers each comprising conductive structures and insulating structures longitudinally adjacent the conductive structures; stadium structures each comprising opposing staircase structures having steps comprising lateral ends of the stacked tiers, at least one opening laterally intervening between at least two of the stadium structures; the at least one opening extending through the stacked tiers and continuously across entire lengths of the at least two stadium structures; conductive contact structures coupled to the conductive structures of the stacked tiers at steps of the opposing staircase structures of at least one of the stadium structures; and conductive routing structures coupled to and extending completely between pairs of the conductive contact structures to form at least one continuous conductive path extending completely across each of the stacked tiers. 
     One of ordinary skill in the art will appreciate that, in accordance with additional embodiments of the disclosure, the features and feature configurations described above in relation to  FIGS.  3 A- 3 F  may be readily adapted to the design needs of different semiconductor devices (e.g., different memory devices, such as different 3D NAND Flash memory devices). By way of non-limiting example,  FIG.  4    illustrates a semiconductor device structure  400  in accordance with another embodiment of the disclosure. The semiconductor device structure  400  may have similar features and functionalities to the semiconductor device structure  300  previously described. However, the semiconductor device structure  400  may, for example, include a relatively greater number of tiers  408 , as well one or more additional features (e.g., additional openings, additional staircase structures, additional conductive contact structures, additional conductive routing structures) and/or feature configurations (e.g., sizes, shapes, arrangements) to account for the relatively greater number of tiers  408 . To avoid repetition, not all features shown in  FIG.  4    are described in detail herein. Rather, unless described otherwise below, features designated by a reference numeral that is a 100 increment of the reference numeral of a feature described previously in relation to one or more of  FIGS.  3 A- 3 F  will be understood to be substantially similar to the feature described previously. 
     As shown in  FIG.  4   , the semiconductor device structure  400  may include a conductive stack structure  426  exhibiting an alternating sequence of insulating structures and conductive structures  428  arranged in tiers  408 . For clarity, the insulating structures of each of the tiers  408  are not depicted  FIG.  4   . However, aside from variances in shape and size, the insulating structures of the conductive stack structure  426  may be substantially similar to, and may be formed and arranged in substantially the manner as, the insulating structures  304  previously described in relation to the conductive stack structure  326 . The conductive stack structure  426  may include a greater number of tiers  408  than the number of the tiers  308  included in the conductive stack structure  326  of the semiconductor device structure  300  previously described in relation to  FIGS.  3 E and  3 F . 
     The conductive stack structure  426  may include multiple (e.g., more than one) staircase structures  420 . For example, the conductive stack structure  426  may include multiple stadium structures  422  each including opposing staircase structures  420 . The multiple stadium structures  422  may be positioned in series and in parallel with one another. By way of non-limiting example, as shown in  FIG.  4   , the conductive stack structure  426  may include a first stadium structure  422   a , a second stadium structure  422   b , a third stadium structure  422   c , a fourth stadium structure  422   d , a fifth stadium structure  422   e , a sixth stadium structure  422   f , a seventh stadium structure  422   g , and an eighth stadium structure  422   h . The first stadium structure  422   a  may include a first forward staircase structure  420   a , and a first reverse staircase structure  420   b  that mirrors the first forward staircase structure  420   a . The second stadium structure  422   b  may extend parallel (e.g., in the X-direction) to the first stadium structure  422   a , and may include a second forward staircase structure  420   c , and a second reverse staircase structure  420   d  that mirrors the second forward staircase structure  420   c . The third stadium structure  422   c  may also extend parallel (e.g., in the X-direction) to the first stadium structure  422   a , and may include a third forward staircase structure  420   e , and a third reverse staircase structure  420   f  that mirrors the third forward staircase structure  420   e . The fourth stadium structure  422   d  may also extend parallel (e.g., in the X-direction) to the first stadium structure  422   a , and may include a fourth forward staircase structure  420   g , and a fourth reverse staircase structure  420   h  that mirrors the fourth forward staircase structure  420   g . The fifth stadium structure  422   e  may extend in series (e.g., in the X-direction) to the first stadium structure  422   a , and may include a fifth forward staircase structure  420   i , and a fifth reverse staircase structure  420   j  that mirrors the fifth forward staircase structure  420   i . The sixth stadium structure  422   f  may extend in parallel (in the X-direction) with the fifth stadium structure  422   e  and in series (e.g., in the X-direction) to the second stadium structure  422   b , and may include a sixth forward staircase structure  420   k , and a sixth reverse staircase structure  420   l  that mirrors the sixth forward staircase structure  420   k . The seventh stadium structure  422   g  may extend in parallel (in the X-direction) with the fifth stadium structure  422   e  and in series (e.g., in the X-direction) to the third stadium structure  422   c , and may include a seventh forward staircase structure  420   m , and a seventh reverse staircase structure  420   n  that mirrors the seventh forward staircase structure  420   m . The eighth stadium structure  422   h  may extend in parallel (in the X-direction) with the fifth stadium structure  422   e  and in series (e.g., in the X-direction) to the fourth stadium structure  422   d , and may include an eighth forward staircase structure  420   o , and an eighth reverse staircase structure  420   p  that mirrors the eighth forward staircase structure  420   o . Each of the stadium structures  422   a  through  422   d  and  422   f  through  422   h  may be at least partially defined by ends of an upper group  409   a  of the tiers  408  (e.g., tiers  408  positioned relatively higher in the Z-direction), and may serve as redundant and/or alternative means of connecting to the tiers  408  of the upper group  409   a . The fifth stadium structure  422   e  may be at least partially defined by ends of a lower group  409   b  of the tiers  408  (e.g., tiers  408  positioned relatively lower in the Z-direction), and may serve as redundant and/or alternative means of connecting to the tiers  408  of the lower group  409   b.    
     In additional embodiments, the conductive stack structure  426  may exhibit one or more of a different number and different configuration of staircase structures  420 . By way of non-limiting example, the conductive stack structure  426  may include a different number (e.g., more or less) of stadium structures  422  associated with (e.g., at least partially defined by ends of) the upper group  409   a  of the tiers  408 , may include one or more additional stadium structures  422  associated with the lower group  409   b  of the tiers  408 , may include one or more additional stadium structures in series with one or more of the stadium structures  422 , may include one or more forward staircase structures but not one or more reverse staircase structures, and/or may include one or more reverse staircase structures but not one or more forward staircase structures. 
     With continued reference to  FIG.  4   , the conductive stack structure  426  may include multiple (e.g., more than one) openings  418  therein. The openings  418  may longitudinally extend (e.g., in the Z-direction) through the conductive stack structure  426 , may laterally intervene (e.g., in the Y-direction) between the staircase structures  420 , and may continuously laterally extend (e.g., in the X-direction) across the entire lengths of the staircase structures  420 . By way of non-limiting example, as shown in  FIG.  4   , the openings  418  may extend completely through each of the tiers  408 , may be positioned laterally adjacent the stadium structures  422 , and may continuously laterally extend across entire lengths of the stadium structures  422 . A first opening  418   a  may be disposed between (e.g., in the Y-direction) and extend across (e.g., in the X-direction) entire lengths of the first stadium structure  422   a  and the second stadium structure  422   b . A second opening  418   b  may extend in parallel with the first opening  418   a , and may be disposed between and extend across entire lengths of the second stadium structure  422   b  and the third stadium structure  422   c . A third opening  418   c  may extend in parallel with the first opening  418   a , and may be disposed between and extend across entire lengths of the third stadium structure  422   c  and the fourth stadium structure  422   d . A fourth opening  418   d  may extend in series with the first opening  418   a , and may be disposed between and extend across entire lengths of the fifth stadium structure  422   e  and the sixth stadium structure  422   f . A fifth opening  418   e  may extend in parallel with the fifth stadium structure  422   e  and series with the second opening  418   b , and may be disposed between and extend across entire lengths of the sixth stadium structure  422   f  and the seventh stadium structure  422   g . A sixth opening  418   f  may extend in parallel with the fifth stadium structure  422   e  and series with the third opening  418   c , and may be disposed between and extend across entire lengths of the seventh stadium structure  422   g  and the eighth stadium structure  422   h . In additional embodiments, the conductive stack structure  426  may include a different number of the openings  418  (e.g., less than six (6) openings  418 , or more than six (6) openings  418 ). 
     As shown in  FIG.  4   , the conductive structures  428  may follow (e.g., route along) lateral (e.g., side) surfaces of the conductive stack structure  426 . For example, the conductive structures  428  may extend into and along outer lateral surfaces (e.g., peripheral lateral surfaces) of the tiers  408 , as well as into and along inner lateral surfaces of the tiers  408  (e.g., lateral surfaces at least partially defined by the openings  418  longitudinally extending through the tiers  408 ). The conductive structures  428  of the upper group  409   a  of the tiers  408  may laterally extend to and partially (e.g., incompletely) around the openings  418 , and may at least partially define a portion of the staircase structures  420  of the conductive stack structure  326 . For example, as shown in  FIG.  4   , one or more (e.g., each) tiers  408  of the upper group  409   a  of the tiers  408  may individually include multiple (e.g., more than one) conductive structures  428  that laterally extend to and partially around the openings  418 , and that partially define the stadium structures  422   a  through  422   d  and  422   f  through  422   h . The multiple conductive structures  428  of each of the tiers  408  defining the stadium structures  422   a  through  422   d  and  422   f  through  422   h  may form discontinuous (e.g., segmented) conductive paths between a first end  432  of the conductive stack structure  426  and a second, opposing end  434  of the conductive stack structure  426 . The first end  432  and the second, opposing end  434  of the conductive stack structure  426  may each be coupled to other components of a semiconductor device (e.g., a memory device) including the semiconductor device structure  400 , such as one or more memory cell arrays (e.g., vertical memory cell arrays). Each of the tiers  408  of the upper group  409   a  of the tiers  408  may include multiple (e.g., more than one) conductive structures  428 , or at least one of the tiers  408  of the upper group  409   a  may include a single (e.g., only one) conductive structure  428 . In addition, the conductive structures  428  of the lower group  409   b  of the tiers  408  may laterally extend to and completely around the openings  418 , and may at least partially define another portion of the staircase structures  420  of the conductive stack structure  326 . For example, as shown in  FIG.  4   , one or more (e.g., each) tiers  408  of the lower group  409   b  of the tiers  408  may individually include one or more conductive structures  428  that laterally extend to and completely around the openings  418 , and that partially define the fifth stadium structure  422   e . The one or more conductive structures  428  of each of the tiers  408  defining the fifth stadium structure  422   e  may form one or more continuous conductive paths between the first end  432  of the conductive stack structure  426  and the second, opposing end  434  of the conductive stack structure  426 . Each of the tiers  408  of the lower group  409   b  of the tiers  408  may include single (e.g., only one) conductive structure  428 , or at least one of the tiers  408  of the lower group  409   b  may include multiple (e.g., more than one) conductive structures  428 . 
     With continued reference to  FIG.  4   , first conductive contact structures  436   a  (e.g., conductive plugs, conductive vertical interconnects) may be coupled (e.g., attached, connected) to at least a portion the conductive structures  428  of the upper group  409   a  of the tiers  408  at opposing steps  424  of one or more of the stadium structures  422 . For example, for each of the tiers  408  of the upper group  409   a  of the tiers  408  defining the stadium structures  422   a  through  422   d , at least one first conductive contact structure  436   a  may be coupled to at least one conductive structure  428  of the tier  408  at a step  424  of at least one forward staircase structure (e.g., one or more of the first forward staircase structure  420   a , the second forward staircase structure  420   c , the third forward staircase structure  420   e , and the fourth forward staircase structure  420   g ), and at least one additional first conductive contact structure  436   a  may be coupled to at least one other conductive structure  428  of the tier  408  at an opposing step  424  of at least one reverse staircase structure (e.g., one or more of the first reverse staircase structure  420   b , the second reverse staircase structure  420   d , the third reverse staircase structure  420   f , and the fourth reverse staircase structure  420   h ). In addition, for each of the tiers  408  of the upper group  409   a  of the tiers  408  defining the stadium structures  422   f  through  422   h , at least one additional first conductive contact structure  436   a  may be coupled to at least one conductive structure  428  of the tier  408  at a step  424  of at least one forward staircase structure (e.g., one or more of the sixth forward staircase structure  420   k , the seventh forward staircase structure  420   m , and the eighth forward staircase structure  420   o ), and at least one further first conductive contact structure  436   a  may be coupled to at least one other conductive structure  428  of the tier  408  at an opposing step  424  of at least one reverse staircase structure (e.g., one or more of the sixth reverse staircase structure  420   l , the seventh reverse staircase structure  420   n , and the eighth reverse staircase structure  420   p ). By way of non-limiting example, as shown in  FIG.  4   , for each of the tiers  408  of the upper group  409   a  of the tiers  408  defining the stadium structures  422   a  through  422   d  and  422   f  through  422   h , two (2) first conductive contact structures  436   a  may be coupled to conductive structures  428  of the tier  408  at opposing steps  424  of the fourth stadium structure  422   d  (e.g., opposing steps  424  of the fourth forward staircase structure  420   g  and the fourth reverse staircase structure  420   h ), and two (2) additional first conductive contact structures  436   a  may be coupled to conductive structures  428  of the tier  408  at opposing steps  424  of the eighth stadium structure  422   h  (e.g., opposing steps  424  of the eighth forward staircase structure  420   o  and the eighth reverse staircase structure  420   p ). 
     In addition, as shown in  FIG.  4   , second conductive contact structures  436   b  may be coupled (e.g., attached, connected) to at least a portion of the conductive structures  428  of each of the upper group  409   a  of the tiers  408  and the lower group of the tiers  408  at steps  424  of the stadium structures  422 . For example, for each of the tiers  408  of the upper group  409   a  of the tiers  408  defining the stadium structures  422   a  through  422   d  and  422   f  through  422   h  at least one second conductive contact structure  436   b  may be coupled to at least one conductive structure  428  of the tier  408  at a step  424  of at least one of the stadium structures  422   a  through  422   d  and  422   f  through  422   h . By way of non-limiting example, for each of the tiers  408  of the upper group  409   a  of the tiers  408  defining the stadium structures  422   a  through  422   d  and  422   f  through  422   h , at least one second conductive contact structure  436   b  may be coupled to at least one conductive structure  428  of the tier  408  at one or more steps  424  of the first stadium structure  422   a  (e.g., a step  424  of the first forward staircase structure  420   a , and/or a step  424  of the first reverse staircase structure  420   b ). In addition, for each of the tiers  408  of the lower group  409   b  defining the fifth stadium structure  422   e  at least one additional second conductive contact structure  436   b  may be coupled to at least one conductive structure  428  of the tier  408  at a step  424  of the fifth stadium structure  422   e . By way of non-limiting example, for each of the tiers  408  of the lower group  409   b  of the tiers  408  defining the fifth stadium structure  422   e , at least one second conductive contact structure  436   b  may be coupled to at least one conductive structure  428  of the tier  408  at one or more steps  424  of the fifth stadium structure  422   e  (e.g., a step  424  of fifth forward staircase structure  420   i , and/or a step  424  of the fifth reverse staircase structure  420   j ). 
     With continued reference to  FIG.  4   , conductive routing structures  438  may be coupled (e.g., attached, connected) to and extend between the first conductive contact structures  436   a . The conductive routing structures  438  may form conductive paths between (e.g., electrically connect) electrically isolated conductive structures  428  of the tiers  408  of the upper group  409   a  of the tiers  408 . For each of the tiers  408  of the upper group  409   a  defining the stadium structures  422   a  through  422   d  and  422   f  through  422   h , the combination of the first conductive contact structures  436   a  and the conductive routing structures  438  may electrically connect a least a portion of conductive structures  428  of the tier  408  to form a continuous conductive path extending from the first end  432  of the conductive stack structure  426  to the second, opposing end  434  of the conductive stack structure  426 . For example, for each of the tiers  408  defining the stadium structures  422   a  through  422   d , at least one conductive routing structure  438  may extend from at least one first conductive contact structure  436   a  located on or over a step  424  of at least one forward staircase structure (e.g., one or more of the first forward staircase structure  420   a , the second forward staircase structure  420   c , the third forward staircase structure  420   e , and the fourth forward staircase structure  420   g ) to at least one other first conductive contact structure  436   a  positioned on or over a step  424  of at least one reverse staircase structure (e.g., one or more of the first reverse staircase structure  420   b , the second reverse staircase structure  420   d , the third reverse staircase structure  420   f , and the fourth reverse staircase structure  420   h ). In addition, for each of the tiers  408  defining the stadium structures  422   f  through  422   h , at least one conductive routing structure  438  may extend from at least one first conductive contact structure  436   a  positioned on or over a step  424  of at least one forward staircase structure (e.g., one or more of the sixth forward staircase structure  420   k , the seventh forward staircase structure  420   m , and the eighth forward staircase structure  420   o ) to at least one other first conductive contact structure  436   a  positioned on or over a step  424  of at least one reverse staircase structure (e.g., one or more of the sixth reverse staircase structure  420   l , the seventh reverse staircase structure  420   n , and the eighth reverse staircase structure  420   p ). By way of non-limiting example, as shown in  FIG.  4   , for each of the tiers  408  of the upper group  409   a  defining the stadium structures  422   a  through  422   d  and  422   f  through  422   h , a conductive routing structure  438  may be coupled to the first conductive contact structures  436   a  located on or over opposing steps  424  of the fourth stadium structure  422   d  (e.g., on or over opposing steps  424  of the fourth forward staircase structure  420   g  and the fourth reverse staircase structure  420   h ), and another conductive routing structure  438  may be coupled to the first conductive contact structures  436   a  located on or over opposing steps  424  of the eighth stadium structure  422   h  (e.g., on or over opposing steps  424  of the eighth forward staircase structure  420   o  and the eighth reverse staircase structure  420   p ). 
     As previously described, tiers  408  (e.g., at least the lower group  409   b  of the tiers  408 ) of the conductive stack structure  426  longitudinally below the tiers  408  defining the stadium structures  422   a  through  422   d  and  422   f  through  422   h  may already exhibit continuous conductive paths extending from the first end  432  of the conductive stack structure  426  to the second, opposing end  434  of the conductive stack structure  426  due to the portions of the conductive structures  428  thereof that extend to and completely around the openings  418 . Accordingly, with the use of the first conductive contact structures  436   a  and the conductive routing structures  438 , each of the tiers  408  of the conductive stack structure  426  may exhibit at least one continuous conductive path extending from the first end  432  of the conductive stack structure  426  to the second, opposing end  434  of the conductive stack structure  426 . 
     As shown in  FIG.  4   , additional conductive routing structures  440  may be coupled (e.g., attached, connected) to and extend between the second conductive contact structures  436   b  and at least one string driver device  442 . The additional conductive routing structures  440  may form conductive paths between (e.g., electrically connect) the string driver device  442  and at least some of the conductive structures  428  of each of the upper group  409   a  of the tiers  408  and the lower group  409   b  of the tiers  408 . For example, for each of the tiers  408  of the upper group  409   a  defining the stadium structures  422   a  through  422   d  and  422   f  through  422   h , at least one additional conductive routing structure  440  may extend from at least one second conductive contact structure  436   b  located on or over a step  424  of one or more of the stadium structures  422   a  through  422   d  and  422   f  through  422   h  (e.g., a step  424  of one or more of the forward staircase structures  420   a ,  420   c ,  420   e ,  420   g ,  420   k ,  420   m , and  420   o , and/or a step  424  of one or more of the reverse staircase structures  420   b ,  420   d ,  420   f ,  420   h ,  4201 ,  420   n , and  420   p ) to at least one of the string driver devices  442 . In addition, for each of the tiers  408  of the lower group  409   b  defining the fifth stadium structure  422   e , at least one other additional conductive routing structure  440  may extend from a step  424  of the fifth stadium structure  422   e  (e.g., a step  424  of the fifth forward staircase structure  420   i , and/or a step  424  of the fifth reverse staircase structure  420   j ) to at least one of the string driver devices  442 . 
     The conductive paths between the one or more string driver devices  442  and the conductive structures  428  of the tiers  408  provided by the second conductive contact structures  436   b  and additional conductive routing structures  440  may facilitate application of voltages to the conductive structures  428  using the string driver devices  442 . In turn, the continuous conductive paths across the conductive stack structure  426  (e.g., from the first end  432  to the second, opposing end  434 ) provided by the configurations and positions of the conductive structures  428 , the first conductive contact structures  436   a , and the conductive routing structures  438  may permit an individual (e.g., single) switching device (e.g., transistor) of the string driver device  442  to drive voltages completely across (e.g., from the first end  432  to the second, opposing end  434 ) and/or in opposing directions across (e.g., toward the first end  432  and toward the second, opposing end  434 ) an individual tier  408  electrically connected thereto. 
     In additional embodiments, one or more of the conductive routing structures  438  and the additional conductive routing structures  440  may be configured and/or positioned differently than depicted in  FIG.  4   . By way of non-limiting example,  FIG.  5    shows an embodiment of a semiconductor device structure  500  including conductive routing structures  538  exhibiting different configurations than the conductive routing structures  438  ( FIG.  4   ). The semiconductor device structure  500  may be substantially similar to the semiconductor device structure  400 , except for the conductive routing structures  538  and the associated positions of at least some of the first conductive contact structures  436   a , the second conductive contact structures  436   b , and the additional conductive routing structure  440 . 
     As shown in  FIG.  5   , in contrast to the configurations and positions of the conductive routing structures  438  ( FIG.  4   ), individual conductive routing structures  538  may be coupled to and extend between first conductive contact structures  436   a  located on or over steps  424  of different stadium structures  422 . For one or more (e.g., each) of the tiers  408  of the upper group  409   a  defining the stadium structures  422   a  through  422   d  and  422   f  through  422   h , one or more conductive routing structures  538  may individually electrically connect conductive structures  428  of different stadium structures  422  (e.g., stadium structures  422  positioned in series with one another) of the tier  408  to form a continuous conductive path extending from the first end  432  of the conductive stack structure  426  to the second, opposing end  434  of the conductive stack structure  426 . For example, for each of the tiers  408  of the upper group  409   a  defining the stadium structures  422   a  through  422   d  and  422   f  through  422   h , at least one conductive routing structure  538  may extend from at least one first conductive contact structure  436   a  located on or over a step  424  of one or more of the stadium structures  422   a  through  422   d  (e.g., a step  424  of one or more of the forward staircase structures  420   a ,  420   c ,  420   e , and  420   g , and/or a step  424  of one or more of the reverse staircase structures  420   b ,  420   d ,  420   f , and  420   h ) to at least one other first conductive contact structure  436   a  located on or over a step  424  of one or more of the stadium structures  422   f  through  422   h  (e.g., a step  424  of one or more of the forward staircase structures  420   k ,  420   m , and  420   o , and/or a step  424  of one or more of the reverse staircase structures  420   l ,  420   n , and  420   p ). By way of non-limiting example, as shown in  FIG.  5   , for each of the tiers  408  of the upper group  409   a  defining the stadium structures  422   a  through  422   d  and  422   f  through  422   h , a conductive routing structure  438  may extend completely between a first conductive contact structure  436   a  located on or over a step  424  of the fourth stadium structure  422   d  (e.g., on or over a step  424  of the fourth forward staircase structure  420   g , or on or over a step  424  of the fourth reverse staircase structure  420   h ) and another first conductive contact structure  436   a  located on or over a step  424  of the eighth stadium structure  422   h  (e.g., on or over a step  424  of the eighth forward staircase structure  420   o , or on or over a step  424  of the eighth reverse staircase structure  420   p ). 
     In addition, as also shown in  FIG.  5   , optionally, at least one of the first conductive contact structures  436   a  located on or over the steps  424  of one or more of stadium structures  422  defined by the upper group  409   a  of the tiers  408  may be shared by at least one of the conductive routing structures  538  and at least one of the additional conductive routing structures  440 . The additional conductive routing structure  440  may be coupled to and extend between to the first conductive contact structure  436   a  and at least one of the string driver devices  442 . By way of non-limiting example, as depicted in  FIG.  5   , at least one of the first conductive contact structures  436   a  located on or over a step  424  of the fourth stadium structure  422   d  may be shared by at least one conductive routing structure  538  extending to at least one of the first conductive contact structures  436   a  located on or over a step  424  of the eighth stadium structure  422   h , and at least one additional conductive routing structure  440  extending to at least one of the string driver devices  442 . Alternative to, or in combination with, sharing one or more of the first conductive contact structures  436   a  between the at least one of the conductive routing structures  538  and at least one of the additional conductive routing structures  440 , one or more of the tiers  408  of the upper group  409   a  may be electrically connected to one or more of the string driver devices  442  in the manner previously described above in relation to  FIG.  4   . 
     Similar to the configuration of the semiconductor device structure  400  ( FIG.  4   ), the configuration of the semiconductor device structure  500  may permit individual switching devices (e.g., individual transistors) of the string driver devices  442  to drive voltages completely across (e.g., from the first end  432  to the second, opposing end  434 ) and/or in opposing directions across (e.g., toward the first end  432  and toward the second, opposing end  434 ) individual tiers  408  of the conductive stack structure  426  electrically connected thereto. 
     Semiconductor devices (e.g., memory devices, such as 3D NAND Flash memory device) including one or more of the semiconductor device structures  100 ,  200 ,  300 ,  400 ,  500  in accordance with embodiments of the disclosure may be used in embodiments of electronic systems of the disclosure. For example,  FIG.  6    is a block diagram of an illustrative electronic system  600  according to embodiments of disclosure. The electronic system  600  may comprise, for example, a computer or computer hardware component, a server or other networking hardware component, a cellular telephone, a digital camera, a personal digital assistant (PDA), portable media (e.g., music) player, a WiFi or cellular-enabled tablet such as, for example, an iPad® or SURFACE® tablet, an electronic book, a navigation device, etc. The electronic system  600  includes at least one memory device  602 . The at least one memory device  602  may include, for example, an embodiment of one or more of the semiconductor device structures  100 ,  200 ,  300 ,  400 ,  500  shown in  FIGS.  1 A through  5    (i.e., including  FIGS.  1 A through  1 G,  2 ,  3 A through  3 F,  4 , and  5   ). The electronic system  600  may further include at least one electronic signal processor device  604  (often referred to as a “microprocessor”). The electronic signal processor device  604  may, optionally, include a semiconductor device structure substantially similar to an embodiment of one or more of the semiconductor device structures  100 ,  200 ,  300 ,  400 ,  500  shown in  FIGS.  1 A through  5    (i.e., including  FIGS.  1 A through  1 G,  2 ,  3 A through  3 F,  4 , and  5   ). The electronic system  600  may further include one or more input devices  606  for inputting information into the electronic system  600  by a user, such as, for example, a mouse or other pointing device, a keyboard, a touchpad, a button, or a control panel. The electronic system  600  may further include one or more output devices  608  for outputting information (e.g., visual or audio output) to a user such as, for example, a monitor, a display, a printer, an audio output jack, a speaker, etc. In some embodiments, the input device  606  and the output device  608  may comprise a single touch screen device that can be used both to input information to the electronic system  600  and to output visual information to a user. The one or more input devices  606  and output devices  608  may communicate electrically with at least one of the memory device  602  and the electronic signal processor device  604 . 
     Thus, in accordance with embodiments of the disclosure, an electronic system comprises at least one semiconductor device structure comprising stacked tiers each comprising at least one conductive structure and at least one insulating structure longitudinally adjacent the at least one conductive structure; at least one stadium structure comprising opposing staircase structures having steps comprising lateral ends of the stacked tiers; at least one opening laterally adjacent the stadium structures, the at least one opening extending through the stacked tiers and continuously across an entire length of the at least one stadium structure; and at least one continuous conductive path at least partially formed by the at least one conductive structure of each of the stacked tiers and extending across an entire length of each of the stacked tiers. 
     The methods and structures of the disclosure may decrease the number of switching devices and interconnections required to drive voltages completely across and/or in different directions across a conductive structure of a tier as compared to conventional methods and structures associated with various semiconductor devices (e.g., memory devices, such as 3D NAND Flash memory). The methods and structures of the disclosure may permit a single switching device to drive an access line (e.g., word line) of a memory cell array from a more centralized (e.g., middle, non-edge) location, which may reduce resistance×current (RC) delay by one-fourth (¼) as compared to conventional methods and structures. The methods and structures of the disclosure may also reduce costs (e.g., manufacturing costs, material costs) and performance, scalability, efficiency, and simplicity as compared to conventional structures and methods. 
     While the disclosure is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, the disclosure is not limited to the particular forms disclosed. Rather, the disclosure is to cover all modifications, equivalents, and alternatives falling within the scope of the following appended claims and their legal equivalent.