Patent Publication Number: US-2023164997-A1

Title: Three dimensional memory device containing resonant tunneling barrier and high mobility channel and method of making the same

Description:
RELATED APPLICATIONS 
     This application is a continuation-in-part (CIP) application of U.S. patent application Ser. No. 17/534,528 filed on Nov. 24, 2021, the entire contents of which are incorporated herein by reference. 
    
    
     FIELD 
     The present disclosure relates generally to the field of semiconductor devices, and particularly to a three-dimensional memory device containing a resonant tunneling barrier and a high mobility channel and methods of manufacturing the same. 
     BACKGROUND 
     Three-dimensional vertical NAND strings having one bit per cell are disclosed in an article by T. Endoh et al., titled “Novel Ultra High Density Memory With A Stacked-Surrounding Gate Transistor (S-SGT) Structured Cell”, IEDM Proc. (2001) 33-36. 
     SUMMARY 
     According to an aspect of the present disclosure, a memory device includes an alternating stack of insulating layers and control gate layers, a memory opening vertically extending through the alternating stack, and a memory opening fill structure containing a memory film and a vertical semiconductor channel located within the memory opening. The memory film includes a resonant tunneling barrier stack, a barrier layer, and a memory material layer located between the resonant tunneling barrier stack and the barrier layer. In one embodiment, the barrier layer may be a dielectric blocking barrier layer. 
     According to another aspect of the present disclosure, a method of making memory device includes forming an alternating stack of insulating layers and control gate layers over a substrate, forming a memory opening vertically extending through the alternating stack, and forming a memory opening fill structure comprising a memory film and a vertical semiconductor channel within the memory opening. The memory film comprises a resonant tunneling barrier stack, a barrier layer, and a memory material layer located between the resonant tunneling barrier stack and the barrier layer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic vertical cross-sectional view of a first exemplary structure after formation of at least one peripheral device, a semiconductor material layer, and a gate dielectric layer according to a first embodiment of the present disclosure. 
         FIG.  2    is a schematic vertical cross-sectional view of the first exemplary structure after formation of an alternating stack of insulating layers and sacrificial material layers according to the first embodiment of the present disclosure. 
         FIG.  3    is a schematic vertical cross-sectional view of the first exemplary structure after formation of stepped terraces and a retro-stepped dielectric material portion according to the first embodiment of the present disclosure. 
         FIG.  4 A  is a schematic vertical cross-sectional view of the first exemplary structure after formation of memory openings and support openings according to the first embodiment of the present disclosure. 
         FIG.  4 B  is a top-down view of the first exemplary structure of  FIG.  4 A . The vertical plane A-A′ is the plane of the cross-section for  FIG.  4 A . 
         FIGS.  5 A- 5 G  are sequential schematic vertical cross-sectional views of a memory opening during formation of a memory opening fill structure according to the first embodiment of the present disclosure. 
         FIG.  6    is a schematic vertical cross-sectional view of a memory opening fill structure according to the first embodiment of the present disclosure 
         FIG.  7    is a schematic vertical cross-sectional view of an alternative embodiment of a memory opening fill structure according to the first embodiment of the present disclosure. 
         FIG.  8    is a schematic vertical cross-sectional view of the first exemplary structure after formation of memory stack structures and support pillar structures according to the first embodiment of the present disclosure. 
         FIG.  9 A  is a schematic vertical cross-sectional view of the first exemplary structure after formation of backside trenches according to the first embodiment of the present disclosure. 
         FIG.  9 B  is a partial see-through top-down view of the first exemplary structure of  FIG.  9 A . The vertical plane A-A′ is the plane of the schematic vertical cross-sectional view of  FIG.  9 A . 
         FIG.  9 C  is a magnified vertical cross-sectional view of a region of the first exemplary structure of  FIG.  9 A . 
         FIG.  10    is a schematic vertical cross-sectional view of the first exemplary structure after formation of backside recesses according to the first embodiment of the present disclosure. 
         FIGS.  11 A- 11 D  are sequential vertical cross-sectional views of a region of the first exemplary structure during formation of electrically conductive layers according to the first embodiment of the present disclosure. 
         FIG.  12 A  is a schematic vertical cross-sectional view of the first exemplary structure after removal of a deposited conductive material from within the backside trench according to the first embodiment of the present disclosure. 
         FIG.  12 B  is a top-down view of the first exemplary structure of  FIG.  12 A . 
         FIG.  12 C  is a magnified view of a region of the first exemplary structure of  FIG.  12 A . 
         FIG.  13    is a schematic vertical cross-sectional view of the first exemplary structure after formation of an insulating spacer and a backside contact structure according to the first embodiment of the present disclosure. 
         FIG.  14 A  is a schematic vertical cross-sectional view of the first exemplary structure after formation of additional contact via structures according to the first embodiment of the present disclosure. 
         FIG.  14 B  is horizontal cross-sectional view along horizontal plane B-B′ of the first exemplary structure of  FIG.  14 A . The vertical plane A-A′ is the plane of the schematic vertical cross-sectional view of  FIG.  14 A . 
         FIG.  14 C  is a magnified view of a region of the first exemplary structure of  FIG.  14 A  that includes a memory opening fill structure. 
         FIG.  14 D  is a magnified view of a region of the first exemplary structure of  FIG.  14 A  that includes an alternative configuration of the memory opening fill structure. 
         FIG.  15 A  is a band diagram of an exemplary memory film and an exemplary vertical semiconductor channel when no voltage is applied to a control gate electrode according to the first embodiment of the present disclosure. 
         FIG.  15 B  is a band diagram of the exemplary memory film and the exemplary vertical semiconductor channel while a negative voltage is applied to the control gate electrode relative to the vertical semiconductor channel according to the first embodiment of the present disclosure. 
         FIG.  15 C  is a band diagram of the exemplary memory film and the exemplary vertical semiconductor channel while a positive voltage is applied to the control gate electrode relative to the vertical semiconductor channel according to the first embodiment of the present disclosure. 
         FIG.  16 A  is a vertical cross-sectional view of a first configuration of a second exemplary structure after formation of a sacrificial cover material layer according to a second embodiment of the present disclosure. 
         FIG.  16 B  is a vertical cross-sectional view of a second configuration of the second exemplary structure after formation of a sacrificial cover material layer according to an embodiment of the present disclosure. 
         FIG.  16 C  is a vertical cross-sectional view of a third configuration of the second exemplary structure after formation of a sacrificial cover material layer according to the second embodiment of the present disclosure. 
         FIGS.  17 A- 17 E  are sequential vertical cross-sectional views of a memory opening in the second exemplary structure during formation of a memory opening fill structure according to the second embodiment of the present disclosure. 
         FIGS.  18 A- 18 F  are sequential vertical cross-sectional views of a region of the second exemplary structure around a memory opening fill structure and a backside trench during formation of electrically conductive layers and contact via structures according to the second embodiment of the present disclosure. 
         FIGS.  19 A- 19 C  are magnified views of various configurations of a region of the exemplary structures in case a backside blocking dielectric layer is employed. 
         FIGS.  20 A- 20 C  are magnified views of various configurations of a region of the exemplary structure in case a backside blocking dielectric layer is not employed. 
         FIG.  21    is a band gap diagram of a layer stack including a vertical semiconductor channel, a memory film, and a word line including a portion of an electrically conductive layer within the second exemplary structure. 
     
    
    
     DETAILED DESCRIPTION 
     As discussed above, the present disclosure is directed to three-dimensional memory devices containing a resonant tunneling barrier and a high mobility channel and methods of making thereof, the various aspects of which are described below. The embodiments of the disclosure can be employed to form various structures including a multilevel memory structure, non-limiting examples of which include semiconductor devices such as three-dimensional memory array devices comprising a plurality of NAND memory strings. 
     The drawings are not drawn to scale. Multiple instances of an element may be duplicated where a single instance of the element is illustrated, unless absence of duplication of elements is expressly described or clearly indicated otherwise. Ordinals such as “first,” “second,” and “third” are employed merely to identify similar elements, and different ordinals may be employed across the specification and the claims of the instant disclosure. The term “at least one” element refers to all possibilities including the possibility of a single element and the possibility of multiple elements. 
     The same reference numerals refer to the same element or similar element. Unless otherwise indicated, elements having the same reference numerals are presumed to have the same composition and the same function. Unless otherwise indicated, a “contact” between elements refers to a direct contact between elements that provides an edge or a surface shared by the elements. If two or more elements are not in direct contact with each other or among one another, the two elements are “disjoined from” each other or “disjoined among” one another. As used herein, a first element located “on” a second element can be located on the exterior side of a surface of the second element or on the interior side of the second element. As used herein, a first element is located “directly on” a second element if there exist a physical contact between a surface of the first element and a surface of the second element. As used herein, a first element is “electrically connected to” a second element if there exists a conductive path consisting of at least one conductive material between the first element and the second element. As used herein, a “prototype” structure or an “in-process” structure refers to a transient structure that is subsequently modified in the shape or composition of at least one component therein. 
     As used herein, a “layer” refers to a material portion including a region having a thickness. A layer may extend over the entirety of an underlying or overlying structure, or may have an extent less than the extent of an underlying or overlying structure. Further, a layer may be a region of a homogeneous or inhomogeneous continuous structure that has a thickness less than the thickness of the continuous structure. For example, a layer may be located between any pair of horizontal planes between, or at, a top surface and a bottom surface of the continuous structure. A layer may extend horizontally, vertically, and/or along a tapered surface. A substrate may be a layer, may include one or more layers therein, or may have one or more layer thereupon, thereabove, and/or therebelow. 
     Generally, a semiconductor die, or a semiconductor package, can include a memory chip. Each semiconductor package contains one or more dies (for example one, two, or four). The die is the smallest unit that can independently execute commands or report status. Each die contains one or more planes (typically one or two). Identical, concurrent operations can take place on each plane, although with some restrictions. Each plane contains a number of blocks, which are the smallest unit that can be erased by in a single erase operation. Each block contains a number of pages, which are the smallest unit that can be programmed, i.e., a smallest unit on which a read operation can be performed. 
     Referring to  FIG.  1   , a first exemplary structure according to the first embodiment of the present disclosure is illustrated, which can be employed, for example, to fabricate a device structure containing vertical NAND memory devices. The first exemplary structure includes a substrate ( 9 ,  10 ), which can be a semiconductor substrate. The substrate can include a substrate semiconductor layer  9  and an optional semiconductor material layer  10 . The substrate semiconductor layer  9  maybe a semiconductor wafer or a semiconductor material layer, and can include at least one elemental semiconductor material (e.g., single crystal silicon wafer or layer), at least one III-V compound semiconductor material, at least one II-VI compound semiconductor material, at least one organic semiconductor material, or other semiconductor materials known in the art. The substrate can have a major surface  7 , which can be, for example, a topmost surface of the substrate semiconductor layer  9 . The major surface  7  can be a semiconductor surface. In one embodiment, the major surface  7  can be a single crystalline semiconductor surface, such as a single crystalline semiconductor surface. 
     As used herein, a “semiconducting material” refers to a material having electrical conductivity in the range from 1.0×10 −6  S/cm to 1.0×10 5  S/cm. As used herein, a “semiconductor material” refers to a material having electrical conductivity in the range from 1.0×10 −6  S/cm to 1.0×10 5  S/cm in the absence of electrical dopants therein, and is capable of producing a doped material having electrical conductivity in a range from 1.0 S/cm to 1.0×10 5  S/cm upon suitable doping with an electrical dopant. As used herein, an “electrical dopant” refers to a p-type dopant that adds a hole to a valence band within a band structure, or an n-type dopant that adds an electron to a conduction band within a band structure. As used herein, a “conductive material” refers to a material having electrical conductivity greater than 1.0×10 5  S/cm. As used herein, an “insulator material” or a “dielectric material” refers to a material having electrical conductivity less than 1.0×10 −6  S/cm. As used herein, a “heavily doped semiconductor material” refers to a semiconductor material that is doped with electrical dopant at a sufficiently high atomic concentration to become a conductive material either as formed as a crystalline material or if converted into a crystalline material through an anneal process (for example, from an initial amorphous state), i.e., to have electrical conductivity greater than 1.0×10 5  S/cm. A “doped semiconductor material” may be a heavily doped semiconductor material, or may be a semiconductor material that includes electrical dopants (i.e., p-type dopants and/or n-type dopants) at a concentration that provides electrical conductivity in the range from 1.0×10 −6  S/cm to 1.0×10 5  S/cm. An “intrinsic semiconductor material” refers to a semiconductor material that is not doped with electrical dopants. Thus, a semiconductor material may be semiconducting or conductive, and may be an intrinsic semiconductor material or a doped semiconductor material. A doped semiconductor material can be semiconducting or conductive depending on the atomic concentration of electrical dopants therein. As used herein, a “metallic material” refers to a conductive material including at least one metallic element therein. All measurements for electrical conductivities are made at the standard condition. 
     At least one semiconductor device  700  for a peripheral circuitry can be formed on a portion of the substrate semiconductor layer  9 . The at least one semiconductor device can include, for example, field effect transistors. For example, at least one shallow trench isolation structure  720  can be formed by etching portions of the substrate semiconductor layer  9  and depositing a dielectric material therein. A gate dielectric layer, at least one gate conductor layer, and a gate cap dielectric layer can be formed over the substrate semiconductor layer  9 , and can be subsequently patterned to form at least one gate structure ( 750 ,  752 ,  754 ,  758 ), each of which can include a gate dielectric  750 , a gate electrode ( 752 ,  754 ), and a gate cap dielectric  758 . The gate electrode ( 752 ,  754 ) may include a stack of a first gate electrode portion  752  and a second gate electrode portion  754 . At least one gate spacer  756  can be formed around the at least one gate structure ( 750 ,  752 ,  754 ,  758 ) by depositing and anisotropically etching a dielectric liner. Active regions  730  can be formed in upper portions of the substrate semiconductor layer  9 , for example, by introducing electrical dopants employing the at least one gate structure ( 750 ,  752 ,  754 ,  758 ) as masking structures. Additional masks may be employed as needed. The active region  730  can include source regions and drain regions of field effect transistors. A first dielectric liner  761  and a second dielectric liner  762  can be optionally formed. Each of the first and second dielectric liners ( 761 ,  762 ) can comprise a silicon oxide layer, a silicon nitride layer, and/or a dielectric metal oxide layer. As used herein, silicon oxide includes silicon dioxide as well as non-stoichiometric silicon oxides having more or less than two oxygen atoms for each silicon atoms. Silicon dioxide is preferred. In an illustrative example, the first dielectric liner  761  can be a silicon oxide layer, and the second dielectric liner  762  can be a silicon nitride layer. The least one semiconductor device for the peripheral circuitry can contain a driver circuit for memory devices to be subsequently formed, which can include at least one NAND device. 
     A dielectric material such as silicon oxide can be deposited over the at least one semiconductor device, and can be subsequently planarized to form a planarization dielectric layer  770 . In one embodiment the planarized top surface of the planarization dielectric layer  770  can be coplanar with a top surface of the dielectric liners ( 761 ,  762 ). Subsequently, the planarization dielectric layer  770  and the dielectric liners ( 761 ,  762 ) can be removed from an area to physically expose a top surface of the substrate semiconductor layer  9 . As used herein, a surface is “physically exposed” if the surface is in physical contact with vacuum, or a gas phase material (such as air). 
     The optional semiconductor material layer  10 , if present, can be formed on the top surface of the substrate semiconductor layer  9  prior to, or after, formation of the at least one semiconductor device  700  by deposition of a single crystalline semiconductor material, for example, by selective epitaxy. The deposited semiconductor material can be the same as, or can be different from, the semiconductor material of the substrate semiconductor layer  9 . The deposited semiconductor material can be any material that can be employed for the substrate semiconductor layer  9  as described above. The single crystalline semiconductor material of the semiconductor material layer  10  can be in epitaxial alignment with the single crystalline structure of the substrate semiconductor layer  9 . Portions of the deposited semiconductor material located above the top surface of the planarization dielectric layer  170  can be removed, for example, by chemical mechanical planarization (CMP). In this case, the semiconductor material layer  10  can have a top surface that is coplanar with the top surface of the planarization dielectric layer  770 . 
     The region (i.e., area) of the at least one semiconductor device  700  is herein referred to as a peripheral device region  200 . The region in which a memory array is subsequently formed is herein referred to as a memory array region  100 . A contact region  300  for subsequently forming stepped terraces of electrically conductive layers can be provided between the memory array region  100  and the peripheral device region  200 . 
     In one alternative embodiment, the peripheral device region  200  containing the at least one semiconductor device  700  for a peripheral circuitry may be located under the memory array region  100  in a CMOS under array configuration. In another alternative embodiment, the peripheral device region  200  may be located on a separate substrate which is subsequently bonded to the memory array region  100 . 
     Referring to  FIG.  2   , a stack of an alternating plurality of first material layers (which can be insulating layers  32 ) and second material layers (which can be sacrificial material layer  42 ) is formed over the top surface of the substrate ( 9 ,  10 ). As used herein, a “material layer” refers to a layer including a material throughout the entirety thereof. As used herein, an alternating plurality of first elements and second elements refers to a structure in which instances of the first elements and instances of the second elements alternate. Each instance of the first elements that is not an end element of the alternating plurality is adjoined by two instances of the second elements on both sides, and each instance of the second elements that is not an end element of the alternating plurality is adjoined by two instances of the first elements on both ends. The first elements may have the same thickness thereamongst, or may have different thicknesses. The second elements may have the same thickness thereamongst, or may have different thicknesses. The alternating plurality of first material layers and second material layers may begin with an instance of the first material layers or with an instance of the second material layers, and may end with an instance of the first material layers or with an instance of the second material layers. In one embodiment, an instance of the first elements and an instance of the second elements may form a unit that is repeated with periodicity within the alternating plurality. 
     Each first material layer includes a first material, and each second material layer includes a second material that is different from the first material. In one embodiment, each first material layer can be an insulating layer  32 , and each second material layer can be a sacrificial material layer. In this case, the stack can include an alternating plurality of insulating layers  32  and sacrificial material layers  42 , and constitutes a prototype stack of alternating layers comprising insulating layers  32  and sacrificial material layers  42 . 
     The stack of the alternating plurality is herein referred to as an alternating stack ( 32 ,  42 ). In one embodiment, the alternating stack ( 32 ,  42 ) can include insulating layers  32  composed of the first material, and sacrificial material layers  42  composed of a second material different from that of insulating layers  32 . The first material of the insulating layers  32  can be at least one insulating material. As such, each insulating layer  32  can be an insulating material layer. Insulating materials that can be employed for the insulating layers  32  include, but are not limited to, silicon oxide (including doped or undoped silicate glass), silicon nitride, silicon oxynitride, organosilicate glass (OSG), spin-on dielectric materials, dielectric metal oxides that are commonly known as high dielectric constant (high-k) dielectric oxides (e.g., aluminum oxide, hafnium oxide, etc.) and silicates thereof, dielectric metal oxynitrides and silicates thereof, and organic insulating materials. In one embodiment, the first material of the insulating layers  32  can be silicon oxide. 
     The second material of the sacrificial material layers  42  is a sacrificial material that can be removed selective to the first material of the insulating layers  32 . As used herein, a removal of a first material is “selective to” a second material if the removal process removes the first material at a rate that is at least twice the rate of removal of the second material. The ratio of the rate of removal of the first material to the rate of removal of the second material is herein referred to as a “selectivity” of the removal process for the first material with respect to the second material. 
     The sacrificial material layers  42  may comprise an insulating material, a semiconductor material, or a conductive material. The second material of the sacrificial material layers  42  can be subsequently replaced with electrically conductive electrodes which can function, for example, as control gate electrodes of a vertical NAND device. Non-limiting examples of the second material include silicon nitride, an amorphous semiconductor material (such as amorphous silicon), and a polycrystalline semiconductor material (such as polysilicon). In one embodiment, the sacrificial material layers  42  can be spacer material layers that comprise silicon nitride or a semiconductor material including at least one of silicon and germanium. 
     In one embodiment, the insulating layers  32  can include silicon oxide, and sacrificial material layers can include silicon nitride sacrificial material layers. The first material of the insulating layers  32  can be deposited, for example, by chemical vapor deposition (CVD). For example, if silicon oxide is employed for the insulating layers  32 , tetraethyl orthosilicate (TEOS) can be employed as the precursor material for the CVD process. The second material of the sacrificial material layers  42  can be formed, for example, CVD or atomic layer deposition (ALD). 
     The sacrificial material layers  42  can be suitably patterned so that conductive material portions to be subsequently formed by replacement of the sacrificial material layers  42  can function as electrically conductive electrodes, such as the control gate electrodes of the monolithic three-dimensional NAND string memory devices to be subsequently formed. The sacrificial material layers  42  may comprise a portion having a strip shape extending substantially parallel to the major surface  7  of the substrate. 
     The thicknesses of the insulating layers  32  and the sacrificial material layers  42  can be in a range from 20 nm to 50 nm, although lesser and greater thicknesses can be employed for each insulating layer  32  and for each sacrificial material layer  42 . The number of repetitions of the pairs of an insulating layer  32  and a sacrificial material layer  42  can be in a range from 2 to 1,024, and typically from 8 to 256, although a greater number of repetitions can also be employed. The sacrificial material layers  42  are replaced with electrically conductive layers that function as control gate electrodes. The top and bottom gate electrodes in the stack may function as the select gate electrodes. In one embodiment, each sacrificial material layer  42  in the alternating stack ( 32 ,  42 ) can have a uniform thickness that is substantially invariant within each respective sacrificial material layer  42 . 
     While the present disclosure is described employing an embodiment in which the spacer material layers are sacrificial material layers  42  that are subsequently replaced with electrically conductive layers, embodiments are expressly contemplated herein in which the sacrificial material layers are formed as electrically conductive layers. In this case, steps for replacing the spacer material layers with electrically conductive layers can be omitted. 
     Optionally, an insulating cap layer  70  can be formed over the alternating stack ( 32 ,  42 ). The insulating cap layer  70  includes a dielectric material that is different from the material of the sacrificial material layers  42 . In one embodiment, the insulating cap layer  70  can include a dielectric material that can be employed for the insulating layers  32  as described above. The insulating cap layer  70  can have a greater thickness than each of the insulating layers  32 . The insulating cap layer  70  can be deposited, for example, by chemical vapor deposition. In one embodiment, the insulating cap layer  70  can be a silicon oxide layer. 
     Referring to  FIG.  3   , stepped surfaces are formed at a peripheral region of the alternating stack ( 32 ,  42 ), which is herein referred to as a terrace region. As used herein, “stepped surfaces” refer to a set of surfaces that include at least two horizontal surfaces and at least two vertical surfaces such that each horizontal surface is adjoined to a first vertical surface that extends upward from a first edge of the horizontal surface, and is adjoined to a second vertical surface that extends downward from a second edge of the horizontal surface. A stepped cavity is formed within the volume from which portions of the alternating stack ( 32 ,  42 ) are removed through formation of the stepped surfaces. A “stepped cavity” refers to a cavity having stepped surfaces. 
     The terrace region is formed in the contact region  300 , which is located between the memory array region  100  and the peripheral device region  200  containing the at least one semiconductor device for the peripheral circuitry. The stepped cavity can have various stepped surfaces such that the horizontal cross-sectional shape of the stepped cavity changes in steps as a function of the vertical distance from the top surface of the substrate ( 9 ,  10 ). In one embodiment, the stepped cavity can be formed by repetitively performing a set of processing steps. The set of processing steps can include, for example, an etch process of a first type that vertically increases the depth of a cavity by one or more levels, and an etch process of a second type that laterally expands the area to be vertically etched in a subsequent etch process of the first type. As used herein, a “level” of a structure including alternating plurality is defined as the relative position of a pair of a first material layer and a second material layer within the structure. 
     Each sacrificial material layer  42  other than a topmost sacrificial material layer  42  within the alternating stack ( 32 ,  42 ) laterally extends farther than any overlying sacrificial material layer  42  within the alternating stack ( 32 ,  42 ) in the terrace region. The terrace region includes stepped surfaces of the alternating stack ( 32 ,  42 ) that continuously extend from a bottommost layer within the alternating stack ( 32 ,  42 ) to a topmost layer within the alternating stack ( 32 ,  42 ). 
     Each vertical step of the stepped surfaces can have the height of one or more pairs of an insulating layer  32  and a sacrificial material layer. In one embodiment, each vertical step can have the height of a single pair of an insulating layer  32  and a sacrificial material layer  42 . In another embodiment, multiple “columns” of staircases can be formed along a first horizontal direction hd 1  such that each vertical step has the height of a plurality of pairs of an insulating layer  32  and a sacrificial material layer  42 , and the number of columns can be at least the number of the plurality of pairs. Each column of staircase can be vertically offset among one another such that each of the sacrificial material layers  42  has a physically exposed top surface in a respective column of staircases. In the illustrative example, two columns of staircases are formed for each block of memory stack structures to be subsequently formed such that one column of staircases provide physically exposed top surfaces for odd-numbered sacrificial material layers  42  (as counted from the bottom) and another column of staircases provide physically exposed top surfaces for even-numbered sacrificial material layers (as counted from the bottom). Configurations employing three, four, or more columns of staircases with a respective set of vertical offsets among the physically exposed surfaces of the sacrificial material layers  42  may also be employed. Each sacrificial material layer  42  has a greater lateral extent, at least along one direction, than any overlying sacrificial material layers  42  such that each physically exposed surface of any sacrificial material layer  42  does not have an overhang. In one embodiment, the vertical steps within each column of staircases may be arranged along the first horizontal direction hd 1 , and the columns of staircases may be arranged along a second horizontal direction hd 2  that is perpendicular to the first horizontal direction hd 1 . In one embodiment, the first horizontal direction hd 1  may be perpendicular to the boundary between the memory array region  100  and the contact region  300 . 
     A retro-stepped dielectric material portion  65  (i.e., an insulating fill material portion) can be formed in the stepped cavity by deposition of a dielectric material therein. For example, a dielectric material such as silicon oxide can be deposited in the stepped cavity. Excess portions of the deposited dielectric material can be removed from above the top surface of the insulating cap layer  70 , for example, by chemical mechanical planarization (CMP). The remaining portion of the deposited dielectric material filling the stepped cavity constitutes the retro-stepped dielectric material portion  65 . As used herein, a “retro-stepped” element refers to an element that has stepped surfaces and a horizontal cross-sectional area that increases monotonically as a function of a vertical distance from a top surface of a substrate on which the element is present. If silicon oxide is employed for the retro-stepped dielectric material portion  65 , the silicon oxide of the retro-stepped dielectric material portion  65  may, or may not, be doped with dopants such as B, P, and/or F. 
     Optionally, drain-select-level isolation structures  72  can be formed through the insulating cap layer  70  and a subset of the sacrificial material layers  42  located at drain select levels. The drain-select-level isolation structures  72  can be formed, for example, by forming drain-select-level isolation trenches and filling the drain-select-level isolation trenches with a dielectric material such as silicon oxide. Excess portions of the dielectric material can be removed from above the top surface of the insulating cap layer  70 . 
     Referring to  FIGS.  4 A and  4 B , a lithographic material stack (not shown) including at least a photoresist layer can be formed over the insulating cap layer  70  and the retro-stepped dielectric material portion  65 , and can be lithographically patterned to form openings therein. The openings include a first set of openings formed over the memory array region  100  and a second set of openings formed over the contact region  300 . The pattern in the lithographic material stack can be transferred through the insulating cap layer  70  or the retro-stepped dielectric material portion  65 , and through the alternating stack ( 32 ,  42 ) by at least one anisotropic etch that employs the patterned lithographic material stack as an etch mask. Portions of the alternating stack ( 32 ,  42 ) underlying the openings in the patterned lithographic material stack are etched to form memory openings  49  and support openings  19 . As used herein, a “memory opening” refers to a structure in which memory elements, such as a memory stack structure, is subsequently formed. As used herein, a “support opening” refers to a structure in which a support structure (such as a support pillar structure) that mechanically supports other elements is subsequently formed. The memory openings  49  are formed through the insulating cap layer  70  and the entirety of the alternating stack ( 32 ,  42 ) in the memory array region  100 . The support openings  19  are formed through the retro-stepped dielectric material portion  65  and the portion of the alternating stack ( 32 ,  42 ) that underlie the stepped surfaces in the contact region  300 . 
     The memory openings  49  extend through the entirety of the alternating stack ( 32 ,  42 ). The support openings  19  extend through a subset of layers within the alternating stack ( 32 ,  42 ). The chemistry of the anisotropic etch process employed to etch through the materials of the alternating stack ( 32 ,  42 ) can alternate to optimize etching of the first and second materials in the alternating stack ( 32 ,  42 ). The anisotropic etch can be, for example, a series of reactive ion etches. The sidewalls of the memory openings  49  and the support openings  19  can be substantially vertical, or can be tapered. The patterned lithographic material stack can be subsequently removed, for example, by ashing. 
     The memory openings  49  and the support openings  19  can extend from the top surface of the alternating stack ( 32 ,  42 ) to at least the horizontal plane including the topmost surface of the semiconductor material layer  10 . In one embodiment, an overetch into the semiconductor material layer  10  may be optionally performed after the top surface of the semiconductor material layer  10  is physically exposed at a bottom of each memory opening  49  and each support opening  19 . The overetch may be performed prior to, or after, removal of the lithographic material stack. In other words, the recessed surfaces of the semiconductor material layer  10  may be vertically offset from the un-recessed top surfaces of the semiconductor material layer  10  by a recess depth. The recess depth can be, for example, in a range from 1 nm to 50 nm, although lesser and greater recess depths can also be employed. The overetch is optional, and may be omitted. If the overetch is not performed, the bottom surfaces of the memory openings  49  and the support openings  19  can be coplanar with the topmost surface of the semiconductor material layer  10 . 
     Each of the memory openings  49  and the support openings  19  may include a sidewall (or a plurality of sidewalls) that extends substantially perpendicular to the topmost surface of the substrate. A two-dimensional array of memory openings  49  can be formed in the memory array region  100 . A two-dimensional array of support openings  19  can be formed in the contact region  300 . The substrate semiconductor layer  9  and the semiconductor material layer  10  collectively constitutes a substrate ( 9 ,  10 ), which can be a semiconductor substrate. Alternatively, the semiconductor material layer  10  may be omitted, and the memory openings  49  and the support openings  19  can be extend to a top surface of the substrate semiconductor layer  9 . Generally, an alternating stack of insulating layers  32  and spacer material layers over a substrate. The spacer material layers are formed as, or are subsequently replaced with, electrically conductive layers. The spacer material layers comprise the sacrificial material layers  42  in case the spacer material layers are subsequently replaced with the electrically conductive layers. 
       FIGS.  5 A- 5 G  are sequential schematic vertical cross-sectional views of a memory opening during formation of a memory opening fill structure according to an embodiment of the present disclosure. 
     Referring to  FIG.  5 A , a memory opening  49  in the exemplary device structure of  FIGS.  4 A and  4 B  is illustrated. The memory opening  49  extends through the insulating cap layer  70 , the alternating stack ( 32 ,  42 ), and optionally into an upper portion of the semiconductor material layer  10 . At this processing step, each support opening  19  can extend through the retro-stepped dielectric material portion  65 , a subset of layers in the alternating stack ( 32 ,  42 ), and optionally through the upper portion of the semiconductor material layer  10 . The recess depth of the bottom surface of each memory opening with respect to the top surface of the semiconductor material layer  10  can be in a range from 0 nm to 30 nm, although greater recess depths can also be employed. Optionally, the sacrificial material layers  42  can be laterally recessed partially to form lateral recesses (not shown), for example, by an isotropic etch. 
     Referring to  FIG.  5 B , an optional pedestal channel portion (e.g., an epitaxial pedestal)  11  can be formed at the bottom portion of each memory opening  49  and each support openings  19 , for example, by selective epitaxy. Each pedestal channel portion  11  comprises a single crystalline semiconductor material in epitaxial alignment with the single crystalline semiconductor material of the semiconductor material layer  10 . In one embodiment, the pedestal channel portion  11  can be doped with electrical dopants of the same conductivity type as the semiconductor material layer  10 . In one embodiment, the top surface of each pedestal channel portion  11  can be formed above a horizontal plane including the top surface of a sacrificial material layer  42 . In this case, at least one source select gate electrode can be subsequently formed by replacing each sacrificial material layer  42  located below the horizontal plane including the top surfaces of the pedestal channel portions  11  with a respective conductive material layer. The pedestal channel portion  11  can be a portion of a transistor channel that extends between a source region to be subsequently formed in the substrate ( 9 ,  10 ) and a drain region to be subsequently formed in an upper portion of the memory opening  49 . A memory cavity  49 ′ is present in the unfilled portion of the memory opening  49  above the pedestal channel portion  11 . In one embodiment, the pedestal channel portion  11  can comprise single crystalline silicon. In one embodiment, the pedestal channel portion  11  can have a doping of the first conductivity type, which is the same as the conductivity type of the semiconductor material layer  10  that the pedestal channel portion contacts. If a semiconductor material layer  10  is not present, the pedestal channel portion  11  can be formed directly on the substrate semiconductor layer  9 , which can have a doping of the first conductivity type. 
     Referring to  FIG.  5 C , a layer stack including a memory film  150  and an optional sacrificial cover material layer  601  can be formed by a series of conformal deposition processes. The memory film  150  includes a resonant tunneling barrier stack  152 , a memory material layer  154 , and a semiconductor barrier layer  156 . 
     The resonant tunneling barrier stack  152  includes at least two semiconductor quantum wells. Each semiconductor quantum well includes a well layer  2 A located between two barrier layers  2 B. The well layer  2 A comprises a semiconductor material having a relatively narrow first bandgap, and the barrier layers  2 B comprise a semiconductor material having a relatively wide second bandgap which is wider than the first bandgap. For example, the well layer  2 A and the barrier layers  2 B of the semiconductor quantum well comprise compound semiconductor layers, such as Group III-V semiconductor layers. In one embodiment, the well layer  2 A may have a direct bandgap less than 1 eV, such as less than 0.5 eV, for example, 0.3 eV to 0.45 eV. For example, the well layer  2 A may comprise indium arsenide, which has a direct bandgap of about 0.36 eV. In one embodiment, the barrier layers  2 B may have a direct bandgap greater than 1.5 eV, such as than greater than 2 eV, for example, 2.1 eV to 2.3 eV. For example, the barrier layers  2 B may comprise aluminum antimonide, which has a direct bandgap of about 2.22 eV. Other semiconductor layers may be used instead of InAs and/or AlSb. In one embodiment, resonant tunneling barrier stack  152  includes two semiconductor quantum wells comprising three wide bandgap semiconductor barrier layers  2 B interlaced with two narrow bandgap semiconductor well layers  2 A. Optionally, an optional InAs interface layer  2 C may be located on a sidewall of the memory opening (i.e., may comprise the outer surface of the resonant tunneling barrier stack  152 ). 
     Each of the barrier layers  2 B may have a thickness in a range from 1 nm to 3 nm, such as from 1.2 nm to 2 nm, although lesser and greater thicknesses may also be employed. Each of the well layers  2 A may have a thickness in a range from 1 nm to 4 nm, such as from 2 nm to 3 nm, although lesser and greater thicknesses may also be employed. In a non-limiting illustrative example, a resonant tunneling barrier stack  152  may comprise, from outside to inside (which corresponds to the order of deposition), an optional semiconductor interface layer  2 C composed of InAs and having a thickness in a range from 1 nm to 1.5 nm, a first semiconductor barrier layer  2 B composed of AlSb and having a thickness of about 1.8 nm, a first semiconductor well layer  2 A composed of InAs and having a thickness of about 3 nm, a second semiconductor barrier layer  2 B composed of AlSb and having a thickness of about 1.2 nm, a second semiconductor well layer  2 A composed of InAs and having a thickness of about 2.4 nm, and a third semiconductor barrier layer  2 B composed of AlSb and having a thickness of about 1.8 nm. 
     The memory material layer  154  can be deposited as a continuous material layer by a conformal deposition process such as a chemical vapor deposition process or an atomic layer deposition process. The memory material layer  154  includes a memory material, i.e., a material that can store data by selecting a state of the material. For example, the memory material layer  154  may include a charge storage material such as silicon nitride, polysilicon, or a metallic material. The memory material layer  154  can be formed as a single memory material layer of homogeneous composition, or can include a stack of multiple memory material layers. In one embodiment, the memory material layer  154  may comprise an insulating charge trapping material, such as one or more silicon nitride segments. The memory material layer  154  can be formed, for example, by chemical vapor deposition (CVD), atomic layer deposition (ALD), physical vapor deposition (PVD), or any suitable deposition technique for storing electrical charges therein. The thickness of the memory material layer  154  can be in a range from 2 nm to 20 nm, although lesser and greater thicknesses can also be employed. In one embodiment, the memory material layer  154  may comprise a charge storage layer consisting essentially of silicon nitride and having a thickness in a range from 4 nm to 6 nm, although lesser and greater thicknesses may also be employed. 
     The semiconductor barrier layer  156  may have a relatively wide bandgap and relatively high thickness which prevents electron tunneling therethrough. Thus, the semiconductor barrier layer  156  may function as a blocking layer in a charge storage NAND device. In one embodiment, the semiconductor barrier layer comprises a compound semiconductor material having a band gap greater than 2 eV. The semiconductor barrier layer  156  may comprise aluminum antimonide have a direct band gap of about 2.22 eV. The thickness of the homogeneous barrier layer  156  may be at least 8 nm, such as in a range from 8 nm to 20 nm, such as from 10 nm to 12 nm, although lesser and greater thicknesses may also be employed. The semiconductor barrier layer  156  may comprise a homogeneous barrier layer having a homogeneous material composition throughout. 
     The optional sacrificial cover material layer  601  includes a sacrificial material that can be subsequently removed selective to the material of the homogeneous barrier layer  156 . In one embodiment, the sacrificial cover material layer  601  can include a semiconductor material such as amorphous silicon, or may include a carbon-based material such as amorphous carbon or diamond-like carbon (DLC). The sacrificial cover material layer  601  can be formed by a conformal deposition method such as low pressure chemical vapor deposition (LPCVD). The thickness of the sacrificial cover material layer  601  can be in a range from 2 nm to 10 nm, although lesser and greater thicknesses can also be employed. A memory cavity  49 ′ is formed in the volume of each memory opening  49  that is not filled with the deposited material layers ( 152 ,  154 ,  156 ,  601 ). 
     Referring to  FIG.  5 D , the optional sacrificial cover material layer  601 , the semiconductor barrier layer  156 , the memory material layer  154 , and the resonant tunneling barrier stack  152  overlying the insulating cap layer  70  are sequentially anisotropically etched employing at least one anisotropic etch process. The portions of the sacrificial cover material layer  601 , the semiconductor barrier layer  156 , the memory material layer  154 , and the resonant tunneling barrier stack  152  located above the top surface of the insulating cap layer  70  can be removed by the at least one anisotropic etch process. Further, the horizontal portions of the sacrificial cover material layer  601 , the semiconductor barrier layer  156 , the memory material layer  154 , and the resonant tunneling barrier stack  152  at a bottom of each memory cavity  49 ′ can be removed to form openings in remaining portions thereof. Each of the sacrificial cover material layer  601 , the semiconductor barrier layer  156 , the memory material layer  154 , and the resonant tunneling barrier stack  152  can be etched by a respective anisotropic etch process employing a respective etch chemistry, which may, or may not, be the same for the various material layers. 
     Each remaining portion of the sacrificial cover material layer  601  can have a tubular configuration. In one embodiment, the memory material layer  154  can include a vertical stack of charge storage regions that store electrical charges upon programming In one embodiment, the memory material layer  154  can be a silicon nitride layer in which each portion adjacent to the sacrificial material layers  42  constitutes a charge storage region. 
     A surface of the pedestal channel portion  11  (or a surface of the semiconductor material layer  10  in case the pedestal channel portions  11  are not employed) can be physically exposed underneath the opening through the sacrificial cover material layer  601 , the semiconductor barrier layer  156 , the memory material layer  154 , and the resonant tunneling barrier stack  152 . Optionally, the physically exposed semiconductor surface at the bottom of each memory cavity  49 ′ can be vertically recessed so that the recessed semiconductor surface underneath the memory cavity  49 ′ is vertically offset from the topmost surface of the pedestal channel portion  11  (or of the semiconductor material layer  10  in case pedestal channel portions  11  are not employed) by a recess distance. A semiconductor barrier layer  156  is located over the memory material layer  154 . A set of a resonant tunneling barrier stack  152 , a memory material layer  154 , and a semiconductor barrier layer  156  in a memory opening  49  constitutes a memory film  150 , which includes a plurality of charge storage regions (as embodied as the memory material layer  154 ) that are insulated from surrounding materials by the resonant tunneling barrier stack  152  and the semiconductor barrier layer  156 . In one embodiment, the sacrificial cover material layer  601 , the semiconductor barrier layer  156 , the memory material layer  154 , and the resonant tunneling barrier stack  152  can have vertically coincident sidewalls. The sacrificial cover material layer  601  can be subsequently removed selective to the material of the semiconductor barrier layer  156 . In case the sacrificial cover material layer  601  includes amorphous silicon, a wet etch process employing hot trimethyl-2 hydroxyethyl ammonium hydroxide (“hot TMY”) or tetramethyl ammonium hydroxide (TMAH) can be performed to remove the sacrificial cover material layer  601 . 
     Referring to  FIG.  5 E , a semiconductor channel layer  60 L can be deposited directly on the semiconductor surface of the pedestal channel portion  11  or the semiconductor material layer  10  if the pedestal channel portion  11  is omitted, and directly on the semiconductor barrier layer  156 . The semiconductor channel layer  60 L includes a semiconductor material such as at least one elemental semiconductor material, at least one III-V compound semiconductor material, at least one II-VI compound semiconductor material, at least one organic semiconductor material, or other semiconductor materials known in the art. In one embodiment, the semiconductor channel layer  60 L includes a high mobility, narrow bandgap semiconductor material such as indium arsenide. Use of a narrow bandgap semiconductor material for the semiconductor channel layer  60 L provides the advantage of enhanced charge carrier mobility in a vertical semiconductor channel The semiconductor channel layer  60 L can have a doping of a first conductivity type (e.g., n-type), which is the same as the conductivity type of the semiconductor material layer  10  and the pedestal channel portions  11 . The semiconductor channel layer  60 L can be formed by a conformal deposition method such as low pressure chemical vapor deposition (LPCVD). The thickness of the semiconductor channel layer  60 L can be in a range from 2 nm to 10 nm, although lesser and greater thicknesses can also be employed. The semiconductor channel layer  60 L may partially fill the memory cavity  49 ′ in each memory opening, or may fully fill the cavity in each memory opening. 
     Referring to  FIG.  5 F , in case the memory cavity  49 ′ in each memory opening is not completely filled by the semiconductor channel layer  60 L, a dielectric core layer  62 L can be deposited in the memory cavity  49 ′ to fill any remaining portion of the memory cavity  49 ′ within each memory opening. Optionally, an interfacial dielectric layer  621  (such as an aluminum oxide layer) having a thickness in a range from 2 nm to 4 nm may be formed prior to formation of the dielectric core layer  62 L. The interfacial dielectric layer  621  can increase the charge carrier mobility in the semiconductor channel layer  60 L. The dielectric core layer  62 L includes a dielectric material, such as silicon oxide or organosilicate glass. The dielectric core layer  62 L can be deposited by a conformal deposition method such as low pressure chemical vapor deposition (LPCVD), or by a self-planarizing deposition process such as spin coating. 
     Referring to  FIG.  5 G , the horizontal portion of the dielectric core layer  62 L (and the interfacial dielectric layer  621 , if present) can be removed, for example, by a recess etch process such that each remaining portions of the dielectric core layer  62 L is located within a respective memory opening  49  and has a respective top surface below the horizontal plane including the top surface of the insulating cap layer  70 . Each remaining portion of the dielectric core layer  62 L constitutes a dielectric core  62 . 
     Referring to  FIG.  6   , a doped semiconductor material having a doping of a second conductivity type can be deposited within each recessed region above the dielectric cores  62 . The deposited semiconductor material can have a doping of a second conductivity type that is the opposite of the first conductivity type. For example, if the first conductivity type is p-type, the second conductivity type is n-type, and vice versa. The dopant concentration in the deposited semiconductor material can be in a range from 5.0×10 18 /cm 3  to 2.0×10 21 /cm 3 , although lesser and greater dopant concentrations can also be employed. 
     Excess portions of the deposited semiconductor material having a doping of the second conductivity type and a horizontal portion of the semiconductor channel layer  60 L can be removed from above the horizontal plane including the top surface of the insulating cap layer  70 , for example, by chemical mechanical planarization (CMP) or a recess etch process. Each remaining portion of the doped semiconductor material having a doping of the second conductivity type constitutes a drain region  63 . Each remaining portion of the semiconductor channel layer  60 L (which has a doping of the first conductivity type) constitutes a vertical semiconductor channel  60 . The vertical semiconductor channel  60  is formed directly on the semiconductor barrier layer  156 . 
     Referring to  FIG.  7   , an alternative embodiment of a memory opening fill structure  58  according to an embodiment of the present disclosure is illustrated, which can be derived from the memory opening fill structure  58  illustrated in  FIG.  6    by reversing the positions of the resonant tunneling barrier stack  152  and the homogeneous barrier layer  156 . Specifically, the homogeneous barrier layer  156  is deposited first, the memory material layer  154  is deposited next, and the resonant tunneling barrier stack  152 . The spatial order and the sequential order of layers within the resonant tunneling barrier stack  152  can be the same as in the first exemplary structure illustrated in  FIG.  5 C . However, the interface layer  2 C may be omitted. 
     In the configuration illustrated in  FIG.  7   , the homogeneous barrier layer  156  (such as an AlSb barrier layer) is located between a charge storage layer (comprising the memory material layer  154 ) and a control gate, i.e., a gate electrode to be subsequently formed by replacing a sacrificial material layer  42  with an electrically conductive layer. The homogeneous barrier layer  156  prevents back tunneling of electrons. The resonant tunneling barrier stack  152  is located between the vertical semiconductor channel  60  and a charge storage layer (comprising the memory material layer  154 ), and enables programming and erase operations by electron tunnelling between the vertical semiconductor channel  60  and the memory material layer  154 . 
     Referring collectively to  FIGS.  6  and  7   , a memory opening fill structure  58  can be formed within each memory opening  49 . The layer stack including a memory film  150  can be a vertically-extending component of the memory opening fill structure  58 . The vertical semiconductor channel  60  can be another vertically-extending component of the memory opening fill structure  58 . The vertical semiconductor channel  60  can be formed on a first side of the layer stack of the memory film  150 . As will be described below, the sacrificial material layers  42  are replaced with a plurality of gate electrodes, which is formed on a second side of the layer stack and are arranged along a lengthwise direction of the vertical semiconductor channel  60 , i.e., along the vertical direction. 
     In one embodiment, the substrate comprises a semiconductor material layer  10 , and a bottom end of the vertical semiconductor channel  60  can be electrically connected to the semiconductor material layer  10 , for example, via a pedestal channel portion  11 . A drain region  63  can be formed at an upper end of the vertical semiconductor channel  60 . 
     Referring to  FIG.  8   , the first exemplary structure is illustrated after formation of memory opening fill structures  58  and support pillar structure  20  within the memory openings  49  and the support openings  19 , respectively. An instance of a memory opening fill structure  58  can be formed within each memory opening  49  of the structure of  FIGS.  4 A and  4 B . An instance of the support pillar structure  20  can be formed within each support opening  19  of the structure of  FIGS.  4 A and  4 B . Each memory stack structure  55  includes a vertical semiconductor channel  60  and a memory film  150 . 
     Referring to  FIGS.  9 A and  9 B , a contact-level dielectric layer  73  can be formed over the alternating stack ( 32 ,  42 ) of insulating layer  32  and sacrificial material layers  42 , and over the memory opening fill structures  58  and the support pillar structures  20 . The contact-level dielectric layer  73  includes a dielectric material that is different from the dielectric material of the sacrificial material layers  42 . For example, the contact-level dielectric layer  73  can include silicon oxide. The contact-level dielectric layer  73  can have a thickness in a range from 150 nm to 1500 nm, although lesser and greater thicknesses can also be employed. 
     A photoresist layer (not shown) can be applied over the contact-level dielectric layer  73 , and is lithographically patterned to form openings in areas between clusters of memory opening fill structures  58 . The pattern in the photoresist layer can be transferred through the contact-level dielectric layer  73 , the alternating stack ( 32 ,  42 ) and/or the retro-stepped dielectric material portion  65  employing an anisotropic etch to form backside trenches  79 , which vertically extend from the top surface of the contact-level dielectric layer  73  at least to the top surface of the substrate ( 9 ,  10 ), and laterally extend through the memory array region  100  and the contact region  300 . 
     In one embodiment, the backside trenches  79  can laterally extend along a first horizontal direction hd 1  and can be laterally spaced apart among one another along a second horizontal direction hd 2  that is perpendicular to the first horizontal direction hd 1 . The memory stack structures  55  can be arranged in rows that extend along the first horizontal direction hd 1 . The drain-select-level isolation structures  72  can laterally extend along the first horizontal direction hd 1 . 
     Each backside trench  79  can have a uniform width that is invariant along the lengthwise direction (i.e., along the first horizontal direction hd 1 ). Each drain-select-level isolation structure  72  can have a uniform vertical cross-sectional profile along vertical planes that are perpendicular to the first horizontal direction hd 1  that is invariant with translation along the first horizontal direction hd 1 . Multiple rows of memory stack structures  55  can be located between a neighboring pair of a backside trench  79  and a drain-select-level isolation structure  72 , or between a neighboring pair of drain-select-level isolation structures  72 . In one embodiment, the backside trenches  79  can include a source contact opening in which a source contact via structure can be subsequently formed. The photoresist layer can be removed, for example, by ashing. 
     A source region  61  can be formed at a surface portion of the semiconductor material layer  10  under each backside trench  79  by implantation of electrical dopants into physically exposed surface portions of the semiconductor material layer  10 . An upper portion of the semiconductor material layer  10  that extends between the source region  61  and the plurality of pedestal channel portions  11  constitutes a horizontal semiconductor channel  59  for a plurality of field effect transistors. 
     The horizontal semiconductor channel  59  is connected to multiple vertical semiconductor channels  60  through respective pedestal channel portions  11 . The horizontal semiconductor channel  59  contacts the source region  61  and the plurality of pedestal channel portions  11 . 
     Referring to  FIGS.  10  and  11 A , an etchant that selectively etches the second material of the sacrificial material layers  42  with respect to the first material of the insulating layers  32  can be introduced into the backside trenches  79 , for example, employing an etch process.  FIG.  11 A  illustrates a region of the first exemplary structure of  FIG.  10   . Backside recesses  43  are formed in volumes from which the sacrificial material layers  42  are removed. The removal of the second material of the sacrificial material layers  42  can be selective to the first material of the insulating layers  32 , the material of the retro-stepped dielectric material portion  65 , the semiconductor material of the semiconductor material layer  10 , and the material of the outermost layer of the memory films  150 . In one embodiment, the sacrificial material layers  42  can include silicon nitride, and the materials of the insulating layers  32  and the retro-stepped dielectric material portion  65  can be selected from silicon oxide and dielectric metal oxides. 
     The etch process that removes the second material selective to the first material and the outermost layer of the memory films  150  can be a wet etch process employing a wet etch solution, or can be a gas phase (dry) etch process in which the etchant is introduced in a vapor phase into the backside trenches  79 . For example, if the sacrificial material layers  42  include silicon nitride, the etch process can be a wet etch process in which the first exemplary structure is immersed within a wet etch tank including phosphoric acid, which etches silicon nitride selective to silicon oxide, silicon, and various other materials employed in the art. The support pillar structure  20 , the retro-stepped dielectric material portion  65 , and the memory opening fill structures  58  provide structural support while the backside recesses  43  are present within volumes previously occupied by the sacrificial material layers  42 . 
     Each backside recess  43  can be a laterally extending cavity having a lateral dimension that is greater than the vertical extent of the cavity. In other words, the lateral dimension of each backside recess  43  can be greater than the height of the backside recess  43 . A plurality of backside recesses  43  can be formed in the volumes from which the second material of the sacrificial material layers  42  is removed. The memory openings in which the memory stack structures  55  are formed are herein referred to as front side openings or front side cavities in contrast with the backside recesses  43 . In one embodiment, the memory array region  100  comprises an array of monolithic three-dimensional NAND strings having a plurality of device levels disposed above the substrate ( 9 ,  10 ). In this case, each backside recess  43  can define a space for receiving a respective word line of the array of monolithic three-dimensional NAND strings. 
     Each of the plurality of backside recesses  43  can extend substantially parallel to the top surface of the substrate ( 9 ,  10 ). A backside recess  43  can be vertically bounded by a top surface of an underlying insulating layer  32  and a bottom surface of an overlying insulating layer  32 . In one embodiment, each backside recess  43  can have a uniform height throughout. 
     Physically exposed surface portions of the optional pedestal channel portions  11  and the semiconductor material layer  10  can be converted into dielectric material portions by thermal conversion and/or plasma conversion of the semiconductor materials into dielectric materials. For example, thermal conversion and/or plasma conversion can be employed to convert a surface portion of each pedestal channel portion  11  into a tubular dielectric spacer  116 , and to convert each physically exposed surface portion of the semiconductor material layer  10  into a planar dielectric portion  616 . In one embodiment, each tubular dielectric spacer  116  can be topologically homeomorphic to a torus, i.e., generally ring-shaped. As used herein, an element is topologically homeomorphic to a torus if the shape of the element can be continuously stretched without destroying a hole or forming a new hole into the shape of a torus. The tubular dielectric spacers  116  include a dielectric material that includes the same semiconductor element as the pedestal channel portions  11  and additionally includes at least one non-metallic element such as oxygen and/or nitrogen such that the material of the tubular dielectric spacers  116  is a dielectric material. In one embodiment, the tubular dielectric spacers  116  can include a dielectric oxide, a dielectric nitride, or a dielectric oxynitride of the semiconductor material of the pedestal channel portions  11 . Likewise, each planar dielectric portion  616  includes a dielectric material that includes the same semiconductor element as the semiconductor material layer and additionally includes at least one non-metallic element such as oxygen and/or nitrogen such that the material of the planar dielectric portions  616  is a dielectric material. In one embodiment, the planar dielectric portions  616  can include a dielectric oxide, a dielectric nitride, or a dielectric oxynitride of the semiconductor material of the semiconductor material layer  10 . 
     Referring to  FIG.  11 B , a backside blocking dielectric layer  44  can be optionally formed. The backside blocking dielectric layer  44 , if present, comprises a dielectric material that functions as a control gate dielectric for the control gates to be subsequently formed in the backside recesses  43 . 
     The backside blocking dielectric layer  44  can be formed in the backside recesses  43  and on a sidewall of the backside trench  79 . The backside blocking dielectric layer  44  can be formed directly on horizontal surfaces of the insulating layers  32  and sidewalls of the memory stack structures  55  within the backside recesses  43 . If the backside blocking dielectric layer  44  is formed, formation of the tubular dielectric spacers  116  and the planar dielectric portion  616  prior to formation of the backside blocking dielectric layer  44  is optional. In one embodiment, the backside blocking dielectric layer  44  can be formed by a conformal deposition process such as atomic layer deposition (ALD). The backside blocking dielectric layer  44  can consist essentially of aluminum oxide. The thickness of the backside blocking dielectric layer  44  can be in a range from 1 nm to 15 nm, such as 2 to 6 nm, although lesser and greater thicknesses can also be employed. 
     The dielectric material of the backside blocking dielectric layer  44  can be a dielectric metal oxide such as aluminum oxide, a dielectric oxide of at least one transition metal element, a dielectric oxide of at least one Lanthanide element, a dielectric oxide of a combination of aluminum, at least one transition metal element, and/or at least one Lanthanide element. Alternatively or additionally, the backside blocking dielectric layer  44  can include a silicon oxide layer. The backside blocking dielectric layer  44  can be deposited by a conformal deposition method such as chemical vapor deposition or atomic layer deposition. The backside blocking dielectric layer  44  is formed on the sidewalls of the backside trenches  79 , horizontal surfaces and sidewalls of the insulating layers  32 , the portions of the sidewall surfaces of the memory stack structures  55  that are physically exposed to the backside recesses  43 , and a top surface of the planar dielectric portion  616 . A backside cavity  79 ′ is present within the portion of each backside trench  79  that is not filled with the backside blocking dielectric layer  44 . 
     Referring to  FIG.  11 C , a metallic barrier layer  46 A can be deposited in the backside recesses  43 . The metallic barrier layer  46 A includes an electrically conductive metallic material that can function as a diffusion barrier layer and/or adhesion promotion layer for a metallic fill material to be subsequently deposited. The metallic barrier layer  46 A can include a conductive metallic nitride material such as TiN, TaN, WN, or a stack thereof, or can include a conductive metallic carbide material such as TiC, TaC, WC, or a stack thereof. In one embodiment, the metallic barrier layer  46 A can be deposited by a conformal deposition process such as chemical vapor deposition (CVD) or atomic layer deposition (ALD). The thickness of the metallic barrier layer  46 A can be in a range from 2 nm to 8 nm, such as from 3 nm to 6 nm, although lesser and greater thicknesses can also be employed. In one embodiment, the metallic barrier layer  46 A can consist essentially of a conductive metal nitride such as TiN. 
     Referring to  FIG.  11 D , a metal fill material is deposited in the plurality of backside recesses  43 , on the sidewalls of the at least one the backside trench  79 , and over the top surface of the contact-level dielectric layer  73  to form a metallic fill material layer  46 B. The metallic fill material can be deposited by a conformal deposition method, which can be, for example, chemical vapor deposition (CVD), atomic layer deposition (ALD), electroless plating, electroplating, or a combination thereof. In one embodiment, the metallic fill material layer  46 B can consist essentially of at least one elemental metal. The at least one elemental metal of the metallic fill material layer  46 B can be selected, for example, from tungsten, cobalt, ruthenium, titanium, and tantalum. In one embodiment, the metallic fill material layer  46 B can consist essentially of a single elemental metal. In one embodiment, the metallic fill material layer  46 B can be deposited employing a fluorine-containing precursor gas such as WF6. In one embodiment, the metallic fill material layer  46 B can be a tungsten layer including a residual level of fluorine atoms as impurities. The metallic fill material layer  46 B is spaced from the insulating layers  32  and the memory stack structures  55  by the metallic barrier layer  46 A, which is a metallic barrier layer that blocks diffusion of fluorine atoms therethrough. 
     A plurality of electrically conductive layers  46  can be formed in the plurality of backside recesses  43 , and a continuous electrically conductive layer  46 L can be formed on the sidewalls of each backside trench  79  and over the contact-level dielectric layer  73 . Each electrically conductive layer  46  includes a portion of the metallic barrier layer  46 A and a portion of the metallic fill material layer  46 B that are located between a vertically neighboring pair of dielectric material layers such as a pair of insulating layers  32 . The continuous electrically conductive layer  46 L includes a continuous portion of the metallic barrier layer  46 A and a continuous portion of the metallic fill material layer  46 B that are located in the backside trenches  79  or above the contact-level dielectric layer  73 . 
     Each sacrificial material layer  42  can be replaced with an electrically conductive layer  46 . A backside cavity  79 ′ is present in the portion of each backside trench  79  that is not filled with the backside blocking dielectric layer  44  and the continuous electrically conductive layer  46 L. A tubular dielectric spacer  116  laterally surrounds a pedestal channel portion  11 . A bottommost electrically conductive layer  46  laterally surrounds each tubular dielectric spacer  116  upon formation of the electrically conductive layers  46 . 
     Referring to  FIGS.  12 A- 12 C , the deposited metallic material of the continuous electrically conductive material layer  46 L is etched back from the sidewalls of each backside trench  79  and from above the contact-level dielectric layer  73 , for example, by an isotropic wet etch, an anisotropic dry etch, or a combination thereof. Each remaining portion of the deposited metallic material in the backside recesses  43  constitutes an electrically conductive layer  46 . Each electrically conductive layer  46  can be a conductive line structure. Thus, the sacrificial material layers  42  are replaced with the electrically conductive layers  46 . 
     Each electrically conductive layer  46  can function as a combination of a plurality of control gate electrodes located at a same level and a word line electrically interconnecting, i.e., electrically shorting, the plurality of control gate electrodes located at the same level. The plurality of control gate electrodes within each electrically conductive layer  46  are the control gate electrodes for the vertical memory devices including the memory stack structures  55 . In other words, each electrically conductive layer  46  can be a word line that functions as a common control gate electrode for the plurality of vertical memory devices. 
     In one embodiment, the removal of the continuous electrically conductive material layer  46 L can be selective to the material of the backside blocking dielectric layer  44 . In this case, a horizontal portion of the backside blocking dielectric layer  44  can be present at the bottom of each backside trench  79 . In another embodiment, the removal of the continuous electrically conductive material layer  46 L may not be selective to the material of the backside blocking dielectric layer  44  or, the backside blocking dielectric layer  44  may not be employed. The planar dielectric portions  616  can be removed during removal of the continuous electrically conductive material layer  46 L. A backside cavity  79 ′ is present within each backside trench  79 . 
     A bottommost electrically conductive layer  46  provided upon formation of the electrically conductive layers  46  within the alternating stack ( 32 ,  46 ) can comprise a select gate electrode for the field effect transistors. Each source region  61  is formed in an upper portion of the semiconductor substrate ( 9 ,  10 ). Semiconductor channels ( 59 ,  11 ,  60 ) extend between each source region  61  and a respective set of drain regions  63 . The semiconductor channels ( 59 ,  11 ,  60 ) include the vertical semiconductor channels  60  of the memory stack structures  55 . 
     Generally, a semiconductor channel such as a vertical semiconductor channel  60  can be formed on a first side of a layer stack including a memory film  150 , and a plurality of control gate electrodes can be formed on a second side of the layer stack. In one embodiment, the plurality of control gate electrodes can comprise portions of the electrically conductive layers  46  that laterally surround the memory opening fill structures  58 . The plurality of gate control electrodes may be arranged along a lengthwise direction of the semiconductor channel such as the vertical direction. 
     Referring to  FIG.  13   , an insulating material layer can be formed in the backside trenches  79  and over the contact-level dielectric layer  73  by a conformal deposition process. Exemplary conformal deposition processes include, but are not limited to, chemical vapor deposition and atomic layer deposition. The insulating material layer includes an insulating material such as silicon oxide, silicon nitride, a dielectric metal oxide, an organosilicate glass, or a combination thereof. In one embodiment, the insulating material layer can include silicon oxide. The insulating material layer can be formed, for example, by low pressure chemical vapor deposition (LPCVD) or atomic layer deposition (ALD). The thickness of the insulating material layer can be in a range from 1.5 nm to 60 nm, although lesser and greater thicknesses can also be employed. 
     If a backside blocking dielectric layer  44  is present, the insulating material layer can be formed directly on surfaces of the backside blocking dielectric layer  44  and directly on the sidewalls of the electrically conductive layers  46 . If a backside blocking dielectric layer  44  is not employed, the insulating material layer can be formed directly on sidewalls of the insulating layers  32  and directly on sidewalls of the electrically conductive layers  46 . 
     An anisotropic etch is performed to remove horizontal portions of the insulating material layer from above the contact-level dielectric layer  73  and at the bottom of each backside trench  79 . Each remaining portion of the insulating material layer constitutes an insulating spacer  74 . A backside cavity  79 ′ is present within a volume surrounded by each insulating spacer  74 . A top surface of the source region  61  can be physically exposed at the bottom of each backside trench  79 . 
     A backside contact via structure  76  can be formed within each backside cavity  79 ′. Each contact via structure  76  can fill a respective cavity  79 ′. The contact via structures  76  can be formed by depositing at least one conductive material in the remaining unfilled volume (i.e., the backside cavity  79 ′) of the backside trench  79 . For example, the at least one conductive material can include a conductive liner  76 A and a conductive fill material portion  76 B. The conductive liner  76 A can include a conductive metallic liner such as TiN, TaN, WN, TiC, TaC, WC, an alloy thereof, or a stack thereof. The thickness of the conductive liner  76 A can be in a range from 3 nm to 30 nm, although lesser and greater thicknesses can also be employed. The conductive fill material portion  76 B can include a metal or a metallic alloy. For example, the conductive fill material portion  76 B can include W, Cu, Al, Co, Ru, Ni, an alloy thereof, or a stack thereof. 
     The at least one conductive material can be planarized employing the contact-level dielectric layer  73  overlying the alternating stack ( 32 ,  46 ) as a stopping layer. If chemical mechanical planarization (CMP) process is employed, the contact-level dielectric layer  73  can be employed as a CMP stopping layer. Each remaining continuous portion of the at least one conductive material in the backside trenches  79  constitutes a backside contact via structure  76 . 
     Alternatively, the above described insulating material layer can be formed in the backside trenches  79  to completely fill the entire volume of a backside trench  79  and may consist essentially of at least one dielectric material. In this alternative embodiment, the source region  61  and the backside trench via structure  76  may be omitted, and a horizontal source line (e.g., direct strap contact) may contact an side of the lower portion of the semiconductor channel  60 . 
     Referring to  FIGS.  14 A- 14 D , additional contact via structures ( 88 ,  86 ,  8 P) can be formed through the contact-level dielectric layer  73 , and optionally through the retro-stepped dielectric material portion  65 . For example, drain contact via structures  88  can be formed through the contact-level dielectric layer  73  on each drain region  63 . Word line contact via structures  86  can be formed on the electrically conductive layers  46  through the contact-level dielectric layer  73 , and through the retro-stepped dielectric material portion  65 . Peripheral device contact via structures  8 P can be formed through the retro-stepped dielectric material portion  65  directly on respective nodes of the peripheral devices. Bit lines  98  are then formed in electrical contact with the drain contact via structures  88 . 
       FIGS.  15 A- 15 C  are band diagrams of an exemplary memory film  150  and an exemplary vertical semiconductor channel  60  of the memory device of  FIG.  14 C .  FIG.  15 A  is a band diagram when no voltage is applied to the control gate electrode  46  according to an embodiment of the present disclosure.  FIG.  15 B  is a band diagram during a programming operation when a negative voltage is applied to the control gate electrode  46  relative to the vertical semiconductor channel  60  according to an embodiment of the present disclosure.  FIG.  15 C  is a band diagram during an erase operation when a positive voltage is applied to the control gate electrode relative to the vertical semiconductor channel according to an embodiment of the present disclosure. 
     As shown in  FIG.  15 A , electrons stored in a charge storage layer  154  are isolated from the vertical semiconductor channel  60  by a very large conduction-band discontinuity between the charge storage layer  154  and the AlSb semiconductor barrier layer  156 . Thus, the relatively thick, wide bandgap semiconductor barrier layer  156  substantially prevents electron tunneling between the vertical semiconductor channel  60  and the charge storage layer  154 . Furthermore, the resonant barrier stack  152  allows elimination, or significant reduction, in the leakage current between the control gate electrode  46  and the charge storage layer  154  due to quantization and difference of electron energy levels in the two quantum well layers  2 AX and  2 AY. For example, the inner well layer  2 AX located closer to the charge storage layer  154  may be thinner than the outer well layer  2 AY located farther from the charge storage layer  154 . Thus, the electron energy levels (i.e., the lowest energy quantum well states) in the inner well layer  2 AX are higher than in the outer well layer  2 AY. Since the electron energy levels do not line up in the two well layers ( 2 AX,  2 AY), substantially no electrons tunnel through the resonant barrier stack  152 . Therefore, when no voltage is applied to the control gate electrode  46 , i.e., when the device is in a thermodynamic equilibrium, electrons are confined inside charge storage layer  154 , the triple resonant-tunnelling barrier stack  152  is opaque to passage of electrons to and from the charge storage layer. 
     Referring to  FIG.  15 B , during a programming operation, a negative voltage is applied to the control gate electrode  46 . This causes the electron energy levels of the two well layers ( 2 AX,  2 AY) to substantially align. This alignment permits resonant quantum tunneling of electrons through the resonant tunneling barrier stack  152 . Thus, the electrons flow from the control gate electrode  46  through the resonant tunneling barrier stack  152  into the charge storage layer  154 . The negative voltage may comprise any suitable voltage sufficient to align the electron energy levels of the well layers to permit resonant quantum tunneling of electrons through the resonant tunneling barrier stack  152 . For example, the negative programming voltage may be in a range from −2.5 V to −3 V. 
     Referring to  FIG.  15 C , during an erase operation, a positive voltage is applied to the control gate electrode. In the illustrated example, the positive erase voltage may be in a range from 2.5 V to 3 V. Band bending and electrical field allow electrons to flow from the charge storage layer  154  to the control gate electrode  46 , thereby removing electrons from the charge storage layer for the erase operation. 
     During a read operation, a positive voltage is applied to the bit lines  98  in a range from 0.5 V to 0.7V, the source region  61  is grounded, and a positive read voltage which is lower than the erase voltage is applied to the control gate electrodes  46 . The read voltage may be in a range from 0.5 V to 1 V. 
     The memory devices of the embodiments of the present disclosure may comprise low voltage, low energy non-volatile memory devices that provide low voltage read/write/erase operations and good charge retention. Electrons stored in the charge storage layer are isolated by a very large conduction-band discontinuity with wide bandgap semiconductor layers (such as AlSb layers). A charge confinement model predicts a room-temperature thermally-activated storage time of an extraordinary 1,014 years for an embodiment of the memory device of the present disclosure. 
     Generally, in conventional 3D-NAND devices, writing and erase operations require application of a large voltage to the control gate electrodes, such as voltages greater than 20 V in magnitude. Program/erase operations in such conventional 3D-NAND devices are relatively slow, and induce voltage-accelerated failure mechanisms in dielectrics limiting endurance of the device. 
     The 3D-NAND structures of the embodiments of the present disclosure provide a non-volatile memory device that is especially suitable for applications requiring extreme low power operations. Lower power consumption is desired for many storage applications, and limits the number of drives that can be run in parallel for concurrent data farming/mining. 
     The embodiment 3D-NAND device is projected to provide a reduction in switching energy per unit area by a factor in a range from 100 to 1,000 compared to DRAM devices and flash memory devices. In some embodiments, the programming and erase voltages may be below 10 V, such as low as only 3˜8 V, and can be chosen as resonant bias voltage for selected composition and geometry of the triple resonant tunneling barrier stack. The read voltages on word lines (control gates) can be then in the range of 1˜3V. Operation voltages can be higher or lower depending on the choice of resonant tunneling barrier stack and its tunneling characteristics. 
     According to an aspect of the present disclosure, a memory device includes an alternating stack of insulating layers  32  and control gate layers  46 , a memory opening  49  vertically extending through the alternating stack ( 32 ,  46 ), and a memory opening fill structure  58  containing a memory film  150  and a vertical semiconductor channel  60  located within the memory opening  49 . The memory film  150  contains a resonant tunneling barrier stack  152 , a semiconductor barrier layer  156 , and a memory material layer  154  located between the resonant tunneling barrier stack  152  and the semiconductor barrier layer  156 . 
     In one embodiment, the resonant tunneling barrier stack  152  comprises at least two semiconductor quantum wells. The least two semiconductor quantum wells comprise an inner quantum well and an outer quantum well located between the inner quantum well and the alternating stack. As shown in  FIG.  15 A , the inner quantum well comprises an inner semiconductor well layer  2 AX located between a first barrier layer  2 B and a second barrier layer  2 B, and the outer quantum well comprises an outer semiconductor well layer  2 AY located between the second barrier layer  2 B and a third barrier layer  2 B. In one embodiment, the inner semiconductor well layer  2 AX is thinner than the outer semiconductor well layer  2 AY. 
     In one embodiment, the inner semiconductor well layer  2 AX and the outer semiconductor well layer  2 AY have a narrower bandgap than the first, second and third barrier layers  2 B. In one embodiment, the inner semiconductor well layer and the outer semiconductor well layer comprise indium arsenide, and the first, second and third barrier layers comprise aluminum antimonide. 
     In one embodiment, the memory material layer  154  comprises a dielectric charge storage material, the vertical semiconductor channel  60  comprises a first compound semiconductor material, and the semiconductor barrier layer  156  comprises a second compound semiconductor material having a wider bandgap than the first compound semiconductor material. In one embodiment, the memory material layer  154  comprises a silicon nitride layer and the vertical semiconductor channel  60  comprises an indium arsenide layer. In one embodiment, the semiconductor barrier layer  156  comprises an aluminum antimonide layer which is thicker than the resonant tunneling barrier stack  152 . 
     In one embodiment shown in  FIG.  14 C , the semiconductor barrier layer  156  is located between the memory material layer  154  and the vertical semiconductor channel  60 , and the resonant tunneling barrier stack  152  is located between the memory material layer  154  and the alternating stack ( 32 ,  46 ). In this embodiment, the semiconductor barrier layer  156  surrounds the vertical semiconductor channel  60 , the memory material layer  154  surrounds the semiconductor barrier layer  156 ; and the resonant tunneling barrier stack  152  surrounds the memory material layer  154 . 
     In an alternative embodiment shown in  FIG.  14 D , the resonant tunneling barrier stack  152  is located between the memory material layer  154  and the vertical semiconductor channel  60 , and the semiconductor barrier layer  156  is located between the memory material layer  154  and the alternating stack ( 32 ,  46 ). In this embodiment, the resonant tunneling barrier stack  152  surrounds the vertical semiconductor channel  60 , the memory material layer  154  surrounds the resonant tunneling barrier stack  152 , and the semiconductor barrier layer  156  surrounds the memory material layer  154 . 
     In one embodiment shown in  FIGS.  15 B and  15 C , a method of operating the memory device includes applying a negative voltage to at least one of the control gate electrodes  46  to program the memory material layer  154 , and applying a positive voltage to at least one of the control gate electrodes  46  to erase the memory material layer  154 . 
       FIGS.  16 A,  16 B, and  16 C  are first, second, and third configurations of a second exemplary structure, respectively, according to a second embodiment of the present disclosure. 
     Referring collectively to  FIGS.  16 A,  16 B, and  16 C , the various configurations of the second exemplary structure can be derived from the alternative embodiment of the first exemplary structure illustrated in  FIGS.  5 C and  14 D  by replacing the semiconductor barrier layer  156  with a dielectric blocking barrier layer  256 . Thus, in the second exemplary structure of the second embodiment, the memory film  250  includes the dielectric blocking barrier layer  256 , the above described memory material layer  154 , and the above described resonant tunneling barrier stack  152 . 
     In one embodiment, the dielectric blocking barrier layer  256  can include at least dielectric material having a sufficiently high band gap and a sufficient thickness to prevent tunneling of electrical charge carriers (such as electrons or holes). In the first configuration illustrated in  FIG.  16 A , the dielectric blocking barrier layer  256  may comprise a layer stack including a dielectric metal oxide layer  258  and a silicon oxide layer  257 . The dielectric metal oxide layer  258  comprises a dielectric metal oxide material, such as aluminum oxide, titanium oxide, tantalum oxide, yttrium oxide, lanthanum oxide, or any other dielectric oxide of at least one transition metal having a dielectric constant greater than 7.9 (which is the dielectric constant of silicon nitride). The dielectric metal oxide layer  258  can be deposited directly on sidewalls of each memory opening  49  by a conformal deposition process, such as a chemical vapor deposition process and/or an atomic layer deposition process. The thickness of the dielectric metal oxide layer  258  may be in a range from 1.5 nm to 6 nm, such as from 2 nm to 3 nm, although lesser and greater thicknesses may also be employed. The silicon oxide layer  257  comprises, and/or consists of, a silicon oxide material, such as undoped silicate glass. The silicon oxide layer  257  can be deposited on the dielectric metal oxide layer  258  by a conformal deposition process such as a chemical vapor deposition process or an atomic layer deposition process. The thickness of the silicon oxide layer  257  may be in a range from 2 nm to 8 nm, such as from 4 nm to 5 nm, although lesser and greater thicknesses may also be employed. 
     In the second configuration illustrated in  FIG.  16 B , the dielectric blocking barrier layer  256  may consist of the dielectric metal oxide layer  258 . The dielectric metal oxide layer  258  comprises a dielectric metal oxide material such as aluminum oxide, titanium oxide, tantalum oxide, yttrium oxide, lanthanum oxide, or any other dielectric oxide of at least one transition metal having a dielectric constant greater than 7.9 (which is the dielectric constant of silicon nitride). The dielectric metal oxide layer  258  can be deposited directly on sidewalls of each memory opening  49  by a conformal deposition process such as a chemical vapor deposition process and/or an atomic layer deposition process. The thickness of the dielectric metal oxide layer  258  may be in a range from 4 nm to 12 nm, such as from 5 nm to 7 nm, although lesser and greater thicknesses may also be employed. 
     In the third configuration illustrated in  FIG.  16 C , the dielectric blocking barrier layer  256  consists of the silicon oxide layer  257 . The silicon oxide layer  257  comprises, and/or consists of, a silicon oxide material, such as undoped silicate glass. The silicon oxide layer  257  can be deposited directly on sidewalls of each memory opening  49  by a conformal deposition process such as a chemical vapor deposition process and/or an atomic layer deposition process. The thickness of the silicon oxide layer  257  may be in a range from 2 nm to 8 nm, such as from 4 nm to 5 nm, although lesser and greater thicknesses may also be employed. 
     The memory material layer  154  can be deposited as a continuous material layer by a conformal deposition process such as a chemical vapor deposition process or an atomic layer deposition process. The memory material layer  154  includes a memory material, i.e., a material that can store data by selecting a state of the material. For example, the memory material layer  154  may include a charge storage material such as silicon nitride, polysilicon, or a metallic material. The memory material layer  154  can be formed as a single memory material layer of homogeneous composition, or can include a stack of multiple memory material layers. In one embodiment, the memory material layer  154  may comprise an insulating charge trapping material, such as one or more silicon nitride segments. The memory material layer  154  can be formed, for example, by chemical vapor deposition (CVD), atomic layer deposition (ALD), physical vapor deposition (PVD), or any suitable deposition technique for storing electrical charges therein. The thickness of the memory material layer  154  can be in a range from 2 nm to 20 nm, although lesser and greater thicknesses can also be employed. In one embodiment, the memory material layer  154  may comprise a charge storage layer consisting essentially of silicon nitride and having a thickness in a range from 4 nm to 6 nm, although lesser and greater thicknesses may also be employed. 
     The resonant tunneling barrier stack  152  comprises at least two semiconductor quantum wells (QW 1 , QW 2 ). In one embodiment, the resonant tunneling barrier stack  152  may comprise a layer stack that includes, from outside to inside, a third barrier layer  2 B, an outer semiconductor well layer  2 A 2 , a second barrier layer  2 B, an inner semiconductor well layer  2 A 1 , and a first barrier layer  2 B. In one embodiment, the least two semiconductor quantum wells (QW 1 , QW 2 ) comprise an inner quantum well QW 1  and an outer quantum well QW 2  located between the inner quantum well QW 1  and the alternating stack ( 32 ,  42 ). In one embodiment, the inner quantum well QW 1  comprises an inner semiconductor well layer  2 A 1  located between a first barrier layer  2 B and a second barrier layer  2 B. In one embodiment, the outer quantum well QW 2  comprises an outer semiconductor well layer  2 A 2  located between the second barrier layer  2 B and a third barrier layer  2 B. The inner semiconductor well layer  2 A 1  is thinner than the outer semiconductor well layer  2 A 2 . 
     The semiconductor well layers ( 2 A 1 ,  2 A 2 ) comprise a semiconductor material having a relatively narrow first bandgap, and the barrier layers  2 B comprise a semiconductor material having a relatively wide second bandgap which is wider than the first bandgap. For example, the semiconductor well layers ( 2 A 1 ,  2 A 2 ) and the barrier layers  2 B of the semiconductor quantum wells (QW 1 , QW 2 ) comprise compound semiconductor layers, such as Group III-V semiconductor layers. In one embodiment, the semiconductor well layers ( 2 A 1 ,  2 A 2 ) may have a direct bandgap less than 1 eV, such as less than 0.5 eV, for example, 0.3 eV to 0.45 eV. For example, the semiconductor well layers ( 2 A 1 ,  2 A 2 ) may comprise indium arsenide, which has a direct bandgap of about 0.36 eV. In one embodiment, the barrier layers  2 B may have a direct bandgap greater than 1.5 eV, such as than greater than 2 eV, for example, 2.1 eV to 2.3 eV. For example, the barrier layers  2 B may comprise aluminum antimonide, which has a direct bandgap of about 2.22 eV. Other semiconductor layers may be used instead of InAs and/or AlSb. In one embodiment, resonant tunneling barrier stack  152  includes two semiconductor quantum wells comprising three wide bandgap semiconductor barrier layers  2 B interlaced with two narrow bandgap semiconductor well layers ( 2 A,  2 B). 
     Each of the barrier layers  2 B may have a thickness in a range from 1 nm to 3 nm, such as from 1.2 nm to 2 nm, although lesser and greater thicknesses may also be employed. Each of the semiconductor well layers ( 2 A 1 ,  2 A 2 ) may have a thickness in a range from 1 nm to 4 nm, such as from 2 nm to 3 nm, although lesser and greater thicknesses may also be employed. In a non-limiting illustrative example, a resonant tunneling barrier stack  152  may comprise, from outside to inside (which corresponds to the order of deposition), a third semiconductor barrier layer  2 B composed of AlSb and having a thickness of about 3.0 nm, an outer semiconductor well layer  2 A 2  composed of InAs and having a thickness of about 3.0 nm, a second semiconductor barrier layer  2 B composed of AlSb and having a thickness of about 1.2 nm, an inner semiconductor well layer  2 A 1  composed of InAs and having a thickness of about 2.4 nm, and a first semiconductor barrier layer  2 B composed of AlSb and having a thickness of about 1.8 nm. 
     Generally, the dielectric blocking barrier layer  256  has a greater band gap than a component layer within the resonant tunneling barrier stack  152 . For example, the dielectric blocking barrier layer  256  can have a greater band gap than the semiconductor well layers ( 2 A 1 ,  2 A 2 ) within the resonant tunneling barrier stack  152 . In one embodiment, the dielectric blocking barrier layer  256  may have a greater band gap than each component layer within the resonant tunneling barrier stack  152 . For example, the dielectric blocking barrier layer  256  can have a greater band gap than the semiconductor wall layers ( 2 A 1 ,  2 A 2 ) and the semiconductor barrier layers  2 B. Upon subsequent replacement of the sacrificial material layers  42  with electrically conductive layers that function as control gate layers, the dielectric blocking barrier layer  256  is formed between the memory material layer  154  and each of the control gate layers. 
     The optional sacrificial cover material layer  601  includes a sacrificial material that can be subsequently removed selective to the material of the barrier layers  2 B. In one embodiment, the sacrificial cover material layer  601  can include a semiconductor material such as amorphous silicon, or may include a carbon-based material such as amorphous carbon or diamond-like carbon (DLC). The sacrificial cover material layer  601  can be formed by a conformal deposition method such as low pressure chemical vapor deposition (LPCVD). The thickness of the sacrificial cover material layer  601  can be in a range from 2 nm to 10 nm, although lesser and greater thicknesses can also be employed. A memory cavity  49 ′ is formed in the volume of each memory opening  49  that is not filled with the deposited material layers ( 152 ,  154 ,  256 ,  601 ). 
       FIGS.  17 A- 17 E  are sequential vertical cross-sectional views of a memory opening  49  in the second exemplary structure during formation of a memory opening fill structure  58  according to an embodiment of the present disclosure. 
     Referring to  FIG.  17 A , the optional sacrificial cover material layer  601 , the resonant tunneling barrier stack  152 , the memory material layer  154 , and the dielectric blocking barrier layer  256  overlying the insulating cap layer  70  are sequentially anisotropically etched employing at least one anisotropic etch process. The portions of the sacrificial cover material layer  601 , the resonant tunneling barrier stack  152 , the memory material layer  154 , and the dielectric blocking barrier layer  256  located above the top surface of the insulating cap layer  70  can be removed by the at least one anisotropic etch process. Further, the horizontal portions of the sacrificial cover material layer  601 , the resonant tunneling barrier stack  152 , the memory material layer  154 , and the dielectric blocking barrier layer  256  at a bottom of each memory cavity  49 ′ can be removed to form openings in remaining portions thereof. Each of the sacrificial cover material layer  601 , the resonant tunneling barrier stack  152 , the memory material layer  154 , and the dielectric blocking barrier layer  256  can be etched by a respective anisotropic etch process employing a respective etch chemistry, which may or may not be the same for the various material layers. 
     Each remaining portion of the sacrificial cover material layer  601  can have a tubular configuration. In one embodiment, the memory material layer  154  can include a vertical stack of charge storage regions that store electrical charges upon programming In one embodiment, the memory material layer  154  can be a silicon nitride layer in which each portion adjacent to the sacrificial material layers  42  constitutes a charge storage region. 
     A surface of the pedestal channel portion  11  (or a surface of the semiconductor material layer  10  in case the pedestal channel portions  11  are not employed) can be physically exposed underneath the opening through the sacrificial cover material layer  601 , the resonant tunneling barrier stack  152 , the memory material layer  154 , and the dielectric blocking barrier layer  256 . Optionally, the physically exposed semiconductor surface at the bottom of each memory cavity  49 ′ can be vertically recessed so that the recessed semiconductor surface underneath the memory cavity  49 ′ is vertically offset from the topmost surface of the pedestal channel portion  11  (or of the semiconductor material layer  10  in case pedestal channel portions  11  are not employed) by a recess distance. A set of a resonant tunneling barrier stack  152 , a memory material layer  154 , and a dielectric blocking barrier layer  256  in a memory opening  49  constitutes a memory film  250 , which includes a plurality of charge storage regions (comprising portions of the memory material layer  154 ) that are insulated from surrounding materials by the resonant tunneling barrier stack  152  and the dielectric blocking barrier layer  256 . In one embodiment, the sacrificial cover material layer  601 , the dielectric blocking barrier layer  256 , the memory material layer  154 , and the resonant tunneling barrier stack  152  can have vertically coincident sidewalls. The sacrificial cover material layer  601  can be subsequently removed selective to the material of the resonant tunneling barrier stack  152 . In case the sacrificial cover material layer  601  includes amorphous silicon, a wet etch process employing hot trimethyl-2 hydroxyethyl ammonium hydroxide (“hot TMY”) or tetramethyl ammonium hydroxide (TMAH) can be performed to remove the sacrificial cover material layer  601 . 
     Referring to  FIG.  17 B , a semiconductor channel layer  60 L can be deposited directly on the semiconductor surface of the pedestal channel portion  11  or the semiconductor material layer  10  if the pedestal channel portion  11  is omitted, and directly on the resonant tunneling barrier stack  152 . The semiconductor channel layer  60 L includes a semiconductor material such as at least one elemental semiconductor material, at least one III-V compound semiconductor material, at least one II-VI compound semiconductor material, at least one organic semiconductor material, or other semiconductor materials known in the art. In one embodiment, the semiconductor channel layer  60 L includes a high mobility, narrow bandgap semiconductor material such as indium arsenide. In one embodiment, the semiconductor channel layer  60 L may consist of a high mobility, narrow bandgap semiconductor material such as indium arsenide. Use of a narrow bandgap semiconductor material for the semiconductor channel layer  60 L provides the advantage of enhanced charge carrier mobility in a vertical semiconductor channel The semiconductor channel layer  60 L can have a doping of a first conductivity type (e.g., n-type), which is the same as the conductivity type of the semiconductor material layer  10  and the pedestal channel portions  11 . The semiconductor channel layer  60 L can be formed by a conformal deposition method such as low pressure chemical vapor deposition (LPCVD). The thickness of the semiconductor channel layer  60 L can be in a range from 2 nm to 10 nm, such as 4 nm to 8 nm, although lesser and greater thicknesses can also be employed. The semiconductor channel layer  60 L may partially fill the memory cavity  49 ′ in each memory opening, or may fully fill the cavity in each memory opening. 
     Referring to  FIG.  17 C , in case the memory cavity  49 ′ in each memory opening is not completely filled by the semiconductor channel layer  60 L, a dielectric core layer  62 L can be deposited in the memory cavity  49 ′ to fill any remaining portion of the memory cavity  49 ′ within each memory opening. Optionally, an interfacial dielectric layer  621  (such as an aluminum oxide layer) having a thickness in a range from 2 nm to 4 nm may be formed prior to formation of the dielectric core layer  62 L. The interfacial dielectric layer  621  can increase the charge carrier mobility in the semiconductor channel layer  60 L. The dielectric core layer  62 L includes a dielectric material, such as silicon oxide or organosilicate glass. The dielectric core layer  62 L can be deposited by a conformal deposition method such as low pressure chemical vapor deposition (LPCVD), or by a self-planarizing deposition process such as spin coating. 
     Referring to  FIG.  17 D , the horizontal portion of the dielectric core layer  62 L (and the interfacial dielectric layer  621 , if present) can be removed, for example, by a recess etch process such that each remaining portions of the dielectric core layer  62 L is located within a respective memory opening  49  and has a respective top surface below the horizontal plane including the top surface of the insulating cap layer  70 . Each remaining portion of the dielectric core layer  62 L constitutes a dielectric core  62 . 
     Referring to  FIG.  17 E , a doped semiconductor material having a doping of a second conductivity type can be deposited within each recessed region above the dielectric cores  62 . The deposited semiconductor material can have a doping of a second conductivity type that is the opposite of the first conductivity type. For example, if the first conductivity type is p-type, the second conductivity type is n-type, and vice versa. The dopant concentration in the deposited semiconductor material can be in a range from 5.0×10 18 /cm 3  to 2.0×10 21 /cm 3 , although lesser and greater dopant concentrations can also be employed. 
     Excess portions of the deposited semiconductor material having a doping of the second conductivity type and a horizontal portion of the semiconductor channel layer  60 L can be removed from above the horizontal plane including the top surface of the insulating cap layer  70 , for example, by chemical mechanical planarization (CMP) or a recess etch process. Each remaining portion of the doped semiconductor material having a doping of the second conductivity type constitutes a drain region  63 . Each remaining portion of the semiconductor channel layer  60 L (which has a doping of the first conductivity type) constitutes a vertical semiconductor channel  60 . The vertical semiconductor channel  60  is formed directly on the resonant tunneling barrier stack  152 . While the inset in  FIG.  17 E  illustrates the first configuration of the second exemplary structure in which the dielectric blocking barrier layer  256  comprises a layer stack including a dielectric metal oxide layer  258  and a silicon oxide layer  257 , embodiments are expressly contemplated herein in which the dielectric blocking barrier layer  256  consists of the dielectric metal oxide layer  258  or the silicon oxide layer  257 , as shown in  FIGS.  16 B and  16 C , respectively. 
     In the second exemplary structure, a memory opening fill structure  58  can be formed within each memory opening  49 . The layer stack including a memory film  250  can be a vertically-extending component of the memory opening fill structure  58 . The vertical semiconductor channel  60  can be another vertically-extending component of the memory opening fill structure  58 . The vertical semiconductor channel  60  can be formed on a first side of the layer stack of the memory film  250 . As will be described below, the sacrificial material layers  42  are replaced with a plurality of gate electrodes, which are formed on a second side of the layer stack and are arranged along a lengthwise direction of the vertical semiconductor channel  60 , i.e., along the vertical direction. 
     In one embodiment, the substrate comprises a semiconductor material layer  10 , and a bottom end of the vertical semiconductor channel  60  can be electrically connected to the semiconductor material layer  10 , for example, via a pedestal channel portion  11 . A drain region  63  can be formed at an upper end of the vertical semiconductor channel  60 . 
     Subsequently, the processing steps described with reference to  FIGS.  9 A- 9 C,  10   , and  11 A can be performed to form a contact-level dielectric layer,  73 , backside trenches  79 , source regions  61 , and backside recesses  43 . The chemistry of the etch step that forms the backside recesses  43  may be modified as needed to minimize collateral etching of the outermost layer of the memory opening fill structures  58 , i.e., the dielectric blocking dielectric layer  250 . 
       FIGS.  18 A- 18 F  are sequential vertical cross-sectional views of a region of the second exemplary structure around a memory opening fill structure  58  and a backside trench  79  during formation of electrically conductive layers  46  and contact via structures ( 88 ,  86 ,  8 P) according to an embodiment of the present disclosure. 
     Referring to  FIG.  18 A , the processing steps of  FIG.  11 A  can be performed to optionally form tubular dielectric spacers  116  and planar dielectric portions  616 . Specifically, physically exposed surface portions of the optional pedestal channel portions  11  and the semiconductor material layer  10  can be converted into dielectric material portions by thermal conversion and/or plasma conversion of the semiconductor materials into dielectric materials. For example, thermal conversion and/or plasma conversion can be employed to convert a surface portion of each pedestal channel portion  11  into a tubular dielectric spacer  116 , and to convert each physically exposed surface portion of the semiconductor material layer  10  into a planar dielectric portion  616 . In one embodiment, the tubular dielectric spacers  116  can include a dielectric oxide, a dielectric nitride, or a dielectric oxynitride of the semiconductor material of the pedestal channel portions  11 . Likewise, each planar dielectric portion  616  includes a dielectric material that includes the same semiconductor element as the semiconductor material layer  10  and additionally includes at least one non-metallic element such as oxygen and/or nitrogen such that the material of the planar dielectric portions  616  is a dielectric material. In one embodiment, the planar dielectric portions  616  can include a dielectric oxide, a dielectric nitride, or a dielectric oxynitride of the semiconductor material of the semiconductor material layer  10 . 
     Referring to  FIG.  18 B , the processing steps of  FIG.  11 B  may be optionally performed to form a backside blocking dielectric layer  44 . The backside blocking dielectric layer  44 , if present, comprises a dielectric material that functions as an additional control gate dielectric for the control gates to be subsequently formed in the backside recesses  43 . The backside blocking dielectric layer  44  is formed directly on cylindrical surface segments of the dielectric blocking barrier layer  256 . 
     The dielectric material of the backside blocking dielectric layer  44  can be a dielectric metal oxide such as aluminum oxide, a dielectric oxide of at least one transition metal element, a dielectric oxide of at least one Lanthanide element, a dielectric oxide of a combination of aluminum, at least one transition metal element, and/or at least one Lanthanide element. In one embodiment, the backside blocking dielectric layer  44  consists essentially of aluminum oxide. For example, if the surface of the dielectric blocking barrier layer  256  comprises silicon oxide, then the backside blocking dielectric layer  44  may be present. Alternatively, if the surface of the dielectric blocking barrier layer  256  comprises aluminum oxide, then the backside blocking dielectric layer  44  may be omitted. 
     Alternatively or additionally, the backside blocking dielectric layer  44  can include a silicon oxide layer. The thickness of the backside blocking dielectric layer  44  may be in a range from 2 nm to 8 nm, such as from 3 nm to 6 nm, although lesser or greater thicknesses may also be employed. The backside blocking dielectric layer  44  can be deposited by a conformal deposition method such as chemical vapor deposition or atomic layer deposition. The backside blocking dielectric layer  44  is formed on the sidewalls of the backside trenches  79 , horizontal surfaces and sidewalls of the insulating layers  32 , the portions of the sidewall surfaces of the memory stack structures  55  that are physically exposed to the backside recesses  43 , and a top surface of the planar dielectric portion  616 . A backside cavity  79 ′ is present within the portion of each backside trench  79  that is not filled with the backside blocking dielectric layer  44 . 
     Referring to  FIG.  18 C , the processing steps of  FIGS.  11 C and  11 D  can be performed. Specifically, a metallic barrier layer  46 A can be deposited in the backside recesses  43 . The metallic barrier layer  46 A includes an electrically conductive metallic material that can function as a diffusion barrier layer and/or adhesion promotion layer for a metallic fill material to be subsequently deposited. The thickness of the metallic barrier layer  46 A can be in a range from 2 nm to 8 nm, such as from 3 nm to 6 nm, although lesser and greater thicknesses can also be employed. In one embodiment, the metallic barrier layer  46 A can consist essentially of a conductive metal nitride such as TiN. 
     A metal fill material is deposited in the plurality of backside recesses  43 , on the sidewalls of the at least one the backside trench  79 , and over the top surface of the contact-level dielectric layer  73  to form the metallic fill material layer  46 B. The metallic fill material can be deposited by a conformal deposition method, which can be, for example, chemical vapor deposition (CVD), atomic layer deposition (ALD), electroless plating, electroplating, or a combination thereof. In one embodiment, the metallic fill material layer  46 B can consist essentially of at least one elemental metal. The at least one elemental metal of the metallic fill material layer  46 B can be selected, for example, from tungsten, cobalt, ruthenium, titanium, and tantalum. In one embodiment, the metallic fill material layer  46 B can consist essentially of a single elemental metal. 
     A plurality of electrically conductive layers  46  can be formed in the plurality of backside recesses  43 , and a continuous electrically conductive layer  46 L can be formed on the sidewalls of each backside trench  79  and over the contact-level dielectric layer  73 . Each electrically conductive layer  46  includes a portion of the metallic barrier layer  46 A and a portion of the metallic fill material layer  46 B that are located between a vertically neighboring pair of dielectric material layers such as a pair of insulating layers  32 . The continuous electrically conductive layer  46 L includes a continuous portion of the metallic barrier layer  46 A and a continuous portion of the metallic fill material layer  46 B that are located in the backside trenches  79  or above the contact-level dielectric layer  73 . 
     Each sacrificial material layer  42  can be replaced with an electrically conductive layer  46 . A backside cavity  79 ′ is present in the portion of each backside trench  79  that is not filled with the backside blocking dielectric layer  44  and the continuous electrically conductive layer  46 L. A tubular dielectric spacer  116  laterally surrounds a pedestal channel portion  11 . A bottommost electrically conductive layer  46  laterally surrounds each tubular dielectric spacer  116  upon formation of the electrically conductive layers  46 . 
     Referring to  FIG.  18 D , the deposited metallic material of the continuous electrically conductive material layer  46 L is etched back from the sidewalls of each backside trench  79  and from above the contact-level dielectric layer  73 , for example, by an isotropic wet etch, an anisotropic dry etch, or a combination thereof. Each remaining portion of the deposited metallic material in the backside recesses  43  constitutes an electrically conductive layer  46 . Each electrically conductive layer  46  can be a conductive line structure. Thus, the sacrificial material layers  42  are replaced with the electrically conductive layers  46 . 
     Each electrically conductive layer  46  can function as a combination of a plurality of control gate electrodes located at a same level and a word line electrically interconnecting, i.e., electrically shorting, the plurality of control gate electrodes located at the same level. The plurality of control gate electrodes within each electrically conductive layer  46  are the control gate electrodes for the vertical memory devices including the memory stack structures  55 . In other words, each electrically conductive layer  46  can be a word line that functions as a common control gate electrode for the plurality of vertical memory devices. 
     In one embodiment, the removal of the continuous electrically conductive material layer  46 L can be selective to the material of the backside blocking dielectric layer  44 . In this case, a horizontal portion of the backside blocking dielectric layer  44  can be present at the bottom of each backside trench  79 . In another embodiment, the removal of the continuous electrically conductive material layer  46 L may not be selective to the material of the backside blocking dielectric layer  44  or, the backside blocking dielectric layer  44  may not be employed. The planar dielectric portions  616  can be removed during removal of the continuous electrically conductive material layer  46 L. A backside cavity  79 ′ is present within each backside trench  79 . 
     At least one bottommost electrically conductive layer  46  provided upon formation of the electrically conductive layers  46  within the alternating stack ( 32 ,  46 ) can comprise a source side select gate electrode. At least one topmost electrically conductive layer  46  provided upon formation of the electrically conductive layers  46  within the alternating stack ( 32 ,  46 ) can comprise a drain side select gate electrode. Each source region  61  is optionally formed in an upper portion of the semiconductor substrate ( 9 ,  10 ). Semiconductor channels ( 59 ,  11 ,  60 ) extend between each source region  61  and a respective set of drain regions  63 . The semiconductor channels ( 59 ,  11 ,  60 ) include the vertical semiconductor channels  60  of the memory stack structures  55 . 
     Generally, a semiconductor channel such as a vertical semiconductor channel  60  can be formed on a first side of a layer stack including a memory film  150 , and a plurality of control gate electrodes can be formed on a second side of the layer stack. In one embodiment, the plurality of control gate electrodes can comprise portions of the electrically conductive layers  46  that laterally surround the memory opening fill structures  58 . The plurality of gate control electrodes are located between the source and drain side select gate electrodes and may be arranged along a lengthwise direction of the semiconductor channel such as the vertical direction. 
     Referring to  FIG.  18 E , the processing steps described with reference to  FIG.  13    can be performed to form an insulating spacer  74  and an optional backside contact via structure  76  (if the source region  61  is present below) in each backside trench  79 . 
     Referring to  FIG.  18 F , the processing steps described with reference to  FIGS.  14 A- 14 D  can be performed to form various additional contact via structures ( 88 ,  86 ,  8 P). 
     Generally, the at least one blocking barrier layer {( 156  or  256 ),  44 } can be provided between a memory material layer  154  and a control gate electrode (which may comprise the electrically conductive layer  46 ). In one embodiment, the at least one blocking dielectric layer {( 156  or  256 ),  44 } may comprise a backside blocking dielectric layer  44  that is formed on a physically exposed surface segment of the memory opening fill structure  58 . 
       FIGS.  19 A- 19 C  are magnified views of various configurations of a region of the exemplary structures in case a backside blocking dielectric layer  44  is employed in the second exemplary structure.  FIG.  19 A  is a magnified view for a first configuration in which the dielectric blocking barrier layer  256  comprises the layer stack including the dielectric metal oxide layer  258  and the silicon oxide layer  257  of  FIG.  16 A .  FIG.  19 B  is a magnified view of a second configuration in which the dielectric blocking barrier layer  256  consists of the dielectric metal oxide layer  258  of  FIG.  16 B .  FIG.  19 C  is a magnified view of a second configuration in which the dielectric blocking barrier layer  256  consists of the silicon oxide layer  257  of  FIG.  16 C . 
       FIGS.  20 A- 20 C  are magnified views of various configurations of a region of the exemplary structure in case the backside blocking dielectric layer  44  is omitted.  FIG.  20 A  is a magnified view for a first configuration in which the dielectric blocking barrier layer  256  comprises the layer stack including the dielectric metal oxide layer  258  and the silicon oxide layer  257  of  FIG.  16 A .  FIG.  20 B  is a magnified view of a second configuration in which the dielectric blocking barrier layer  256  consists of the dielectric metal oxide layer  258  of  FIG.  16 A .  FIG.  20 C  is a magnified view of a second configuration in which the dielectric blocking barrier layer  256  consists of the silicon oxide layer  257  of  FIG.  16 C . 
       FIG.  21    is a band gap diagram of a layer stack including a vertical semiconductor channel  60 , a memory film  250 , and a control gate  46  within the second exemplary structure. The band diagram is illustrated for an illustrative case in which the dielectric blocking barrier layer  256  includes the silicon oxide layer  257  and the aluminum oxide layer  258 . As discussed above, various other combinations of one or more dielectric materials may be employed for the dielectric blocking barrier layer  256 . 
     Charge carriers (e.g., electrons or holes) stored in the memory material layer  154  (e.g., silicon nitride) are isolated by a dielectric blocking barrier layer  256  on one side, and the resonant tunneling barrier  152  on the other side. The dielectric blocking barrier layer  256  may comprise a wide band gap dielectric material (e.g. aluminum oxide) or dielectric stack (e.g. aluminum oxide and silicon oxide). Thus, charge carrier may be stored in the memory material layer  154  for many dozens of years, 
     The use of a dielectric blocking barrier layer  256  instead of III-V semiconductor barrier layer  156  in the first embodiment provides robust blocking for both electrons and holes, and hence better reliability. In addition, the memory film  250  of the second embodiment does not require negative control gate bias operation, simplifying design and reducing chip area. Furthermore, the device of the second embodiment allows both substrate/well erase operation (for devices in which the channel  60  is electrically connected to the substrate ( 9 ,  10 )) or gate induced drain leakage (GIDL) type erase (for devices in which the channel is not electrically connected to the substrate). For example, GIDL erase may be used in a driver circuit CMOS under memory array configuration device which uses a direct strap source layer which contacts a side of the channel, or in a driver circuit CMOS bonded to the memory array configuration device in which the memory array substrate may be removed and a top source contact is formed on exposed bottom tips of the channels after the bonding step. 
     For example, the memory cell of the second embodiment may be programmed by applying a positive bias to its control gate  46  (e.g., a bias of +2.5V to 3V). The thickness of the quantum wells in the resonant tunneling barrier  152  may be selected in such a way that available electron energy levels line up at certain voltage applied to control gate  46 , e.g. 2.5V. Once energy levels in the quantum wells are nearly coincident, it leads to a strong coupling of these states and resonant tunnelling, and electrons flow from the semiconductor channel  60  to the memory material layer  154  to charge the memory cell. 
     The memory cell of the second embodiment may be erased by applying a positive bias to the semiconductor channel  60  (e.g., a bias of +2.5V to 8V, such as 2.5V to 3V, or 3V to 8V). If the semiconductor channel  60  is electrically connected to the substrate ( 9 ,  10 ), then the erase voltage may be applied to the substrate. 
     If the semiconductor channel  60  is not electrically connected to the substrate ( 9 ,  10 ), then the semiconductor channel  60  potential can be raised using GIDL. For example, the source line and/or the bit line of the memory cell being erased is biased at relatively high positive voltage (e.g., 3V to 8V), while the source side and/or the drain side select gate electrodes are allowed to float at about zero volts. Band bending and the electric field allow electrons to flow from the memory material layer  154  portion of the memory cell to the semiconductor channel  60  while holes flow from the semiconductor channel to the memory material layer  154  portion of the memory cell to facilitate erasing the cell. The dielectric blocking barrier layer  156  prevents or reduces electron and hole back leakage into the control gate  46  due to big band offsets in both of the dielectric blocking barrier layer conduction and valence bands. The device of the second embodiment may be read using any suitable NAND memory device reading operation. 
     Referring to all drawings and according to various embodiments of the present disclosure, a memory device is provided, which comprises: an alternating stack of insulating layers  32  and control gate layers  46 ; a memory opening  49  vertically extending through the alternating stack; and a memory opening fill structure  58  comprising a memory film ( 150  or  250 ) and a vertical semiconductor channel  60  located within the memory opening  49 , wherein the memory film ( 150  or  250 ) comprises a resonant tunneling barrier stack  152 , a barrier layer ( 156  or  256 ), and a memory material layer  154  located between the resonant tunneling barrier stack and the barrier layer. 
     In the second embodiment, the barrier layer comprises a dielectric blocking barrier layer  256 . 
     In one embodiment, the resonant tunneling barrier stack  152  comprises at least two semiconductor quantum wells (QW 1 , QW 2 ). In one embodiment, the at least two semiconductor quantum wells (QW 1 , QW 2 ) comprise an inner quantum well QW 1  and an outer quantum well QW 2  located between the inner quantum well QW 1  and the alternating stack. In one embodiment, the inner quantum well QW 1  comprises an inner semiconductor well layer  2 A 1  located between a first barrier layer  2 B and a second barrier layer  2 B; and the outer quantum well QW 2  comprises an outer semiconductor well layer  2 A 2  located between the second barrier layer  2 B and a third barrier layer  2 B. 
     In one embodiment, the inner semiconductor well layer  2 A 1  is thinner than the outer semiconductor well layer  2 A 2 . In one embodiment, the inner semiconductor well layer  2 A 1  and the outer semiconductor well layer  2 A 2  have a narrower bandgap than the first, second and third barrier layers  2 B. In one embodiment, the inner semiconductor well layer  2 A 1  and the outer semiconductor well layer  2 A 2  comprise indium arsenide, and the first, second and third barrier layers  2 B comprise aluminum antimonide. 
     In one embodiment, the memory material layer  154  comprises a dielectric charge storage material, the vertical semiconductor channel  60  comprises a first compound semiconductor material. In the second embodiment, the dielectric blocking barrier layer has a greater band gap than a component layer within the resonant tunneling barrier stack, greater than the first compound semiconductor material and greater the dielectric charge storage material. 
     In one embodiment shown in  FIGS.  19 B and  20 B , the dielectric blocking barrier layer  156  comprises a dielectric metal oxide layer  158  located inside the memory opening  49 . In another embodiment shown in  FIGS.  19 A and  20 A , the dielectric blocking barrier layer  156  further comprises a silicon oxide layer  156  located inside the memory opening  49 . 
     In another embodiment shown in  FIG.  19 C , the dielectric blocking barrier layer  156  comprises a silicon oxide layer  156  located inside the memory opening  49 , and a dielectric metal oxide layer  44  located outside the memory opening and comprising an upper horizontally-extending portion, a lower horizontally-extending portion, and a tubular portion connecting the upper horizontally-extending portion and the lower horizontally extending portion and laterally surrounding the memory opening fill structure  58 . 
     In one embodiment, the resonant tunneling barrier stack  152  surrounds the vertical semiconductor channel  60 ; the memory material layer  154  surrounds the resonant tunneling barrier stack  152 ; and the at least one blocking barrier layer ( 156  or  256 ) surrounds the memory material layer  154 . 
     In one embodiment, the memory device of the second embodiment of the present disclosure may be operated by applying a positive voltage to at least one of the control gate electrodes to program the memory material layer  154 ; and applying a positive voltage to the semiconductor channel to erase the memory material layer  154 . 
     The various embodiments of the present disclosure may be employed to provide a three-dimensional memory device employing resonant tunneling through a resonant tunneling barrier stack  152 , which enables a low voltage operation for a charge storage memory devices through use of resonant tunneling of charge carriers through quantum wells having aligned energy states. 
     Although the foregoing refers to particular preferred embodiments, it will be understood that the disclosure is not so limited. It will occur to those of ordinary skill in the art that various modifications may be made to the disclosed embodiments and that such modifications are intended to be within the scope of the disclosure. Compatibility is presumed among all embodiments that are not alternatives of one another. The word “comprise” or “include” contemplates all embodiments in which the word “consist essentially of” or the word “consists of” replaces the word “comprise” or “include,” unless explicitly stated otherwise. Where an embodiment employing a particular structure and/or configuration is illustrated in the present disclosure, it is understood that the present disclosure may be practiced with any other compatible structures and/or configurations that are functionally equivalent provided that such substitutions are not explicitly forbidden or otherwise known to be impossible to one of ordinary skill in the art. All of the publications, patent applications and patents cited herein are incorporated herein by reference in their entirety.