Patent Abstract:
An electronically scannable multiplexing device is capable of addressing multiple bits within a volatile or non-volatile memory cell. The multiplexing device generates an electronically scannable conducting channel with two oppositely formed depletion regions. The depletion width of each depletion region is controlled by a voltage applied to a respective control gate at each end of the multiplexing device. The present multi-bit addressing technique allows, for example, 10 to 100 bits of data to be accessed or addressed at a single node. The present invention can also be used to build a programmable nanoscale logic array or for randomly accessing a nanoscale sensor array.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a continuation application which is based upon and claims priority from prior and claims priority from prior U.S. Pat. Ser. No. 12/338,275, filed on Dec. 18, 2008, now U.S. Pat. No. 7,795,044, which is a continuation application of U.S. Pat. Ser. No. 11/926,031, filed on Oct. 28, 2007, now U.S. Pat. No. 7,514,327, which is a divisional of prior U.S. patent Ser. No. 11/117,276, filed on Apr. 27, 2005, now U.S. Pat. No. 7,352,029, each of the aforementioned patent applications is herein incorporated by reference in their entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention generally relates to the field of semiconductor devices. More specifically, the present invention relates to a semiconductor multiplexing device that generates an electronically scannable conducting channel with two oppositely formed depletion regions. The multiplexing device has numerous applications. For example, the multiplexing device could be used to address multiple bits within a memory cell, or to connect nano lines to micro lines within a minimal space or could be used to build a nanoscale programmable logic array or to perform chemical and/or biological sensing at the nanoscale (molecular) level. 
     BACKGROUND OF THE INVENTION 
     Conventional memory devices are limited to mostly 1 bit at the intersection of a wordline (WL) and a bitline (BL) in a memory array. For example, DRAM devices are limited to 1 bit per intersection, which corresponds to the presence of only one capacitor at each node. Similarly, FLASH devices have at most 2 bits per cell, in a multibit or multilevel configuration. These 2 bits can be detected based on the magnitude and direction of the current flow across the cell. 
     However, conventional memory devices are not capable of easily accommodating more than two memory bits at every crosspoint intersection. It would therefore be desirable to expand the access capability in memory devices to select or read multiple bits at every memory area or crosspoint that is normally desired by one memory wordline and bitline. 
     One problem facing conventional semiconductor lithographic techniques is the ability to electrically interconnect nano-scaled lines or patterns (on the order of 1 nm to 100 nm) and micro-scaled lines or patterns (on the order of 90 nm or a feature that could be typically defined by semiconductor processes such as lithography). Such connection is not currently practical, as it requires a significant interconnect semiconductor area, which increases the cost and complexity of the manufacturing process or the final product. 
     It would therefore be desirable to have a multiplexing device or an addressing device that establishes selective contact to memory cells, logic devices, sensors, or between nano-scaled lines and micro-scaled lines within a minimal space, thus limiting the overall cost and complexity of the final product. 
     The need for such a multiplexing device has heretofore remained unsatisfied. 
     SUMMARY OF THE INVENTION 
     The present invention satisfies this need, and presents a multiplexing device capable of selectively addressing multiple nodes or cross-points, such as multiple bits within a volatile or non-volatile memory cell. This multi-node addressing aspect of the present invention uses the fact that wordline and bitline voltages can be varied in a continuous fashion, to enable the selection or reading of multiple states at every crosspoint. 
     The present multi-node addressing technique allows, for example, 10 to 100 bits of data to be recorded at a single node, or in general to access bits of data that are of the order of 100 times more densely packed than conventional lithographically defined lines. As used herein, a node includes for example the intersection of a wordline and a bitline, such as a memory wordline and bitline. 
     The multiplexing devices selectively generates a thin, elongated, semiconducting (or conducting) channel (or window) at a desired location within a substrate, to enable control of the width of the channel, from a first conducting sea of electrons on one side of the substrate to a second conducting sea of electrons on the other side of the substrate. 
     In one embodiment, the multiplexing device generates an electronically scannable conducting channel with two oppositely formed depletion regions. The depletion width of each depletion region is controlled by a voltage (or potential) applied to a respective control gate at each end of the multiplexing device. 
     In another embodiment, the depletion width is controlled from one control gate only, allowing the access to the memory bits for both the reading and writing operations to be sequential. Other embodiments are also contemplated by the present invention. 
     If the depletion width is controlled at both ends of the multiplexing device, along the same axis, the conducting channel can be small (e.g., sub 10 nm) to enable random access to the memory bits. This embodiment is applicable to random access memories, such as SRAM, DRAM, and FLASH, for embedded and standalone applications and to programmable logic arrays. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The various features of the present invention and the manner of attaining them will be described in greater detail with reference to the following description, claims, and drawings, wherein reference numerals are reused, where appropriate, to indicate a correspondence between the referenced items, and wherein: 
         FIG. 1  is a schematic illustration of an exemplary multiplexing device of the present invention, comprising a scannable conducting channel having a relatively narrow width, shown in a first position within a scanning region; 
         FIG. 2  is a schematic illustration of the multiplexing device of  FIG. 1 , showing the scannable conducting channel with a relatively wider width, in a second position within the scanning region; 
         FIG. 3  is a schematic illustration of another embodiment of the multiplexing device of  FIGS. 1 and 2 , wherein the scannable conducting channel connects conducting lines, such as nano-scaled lines, on one side of the multiplexing device to electrodes on the opposite side of the multiplexing device; 
         FIG. 4  is a schematic illustration of yet another embodiment of the multiplexing device of  FIG. 3 , wherein the scannable conducting channel connects conducting lines, such as nano-scaled lines, on one side of the multiplexing device to other conducting lines, such as nano-scaled lines, on the opposite side of the multiplexing device; 
         FIG. 5  is a schematic illustration of still another embodiment of the multiplexing device of  FIG. 4 , wherein the scannable conducting channel connects conducting lines, such as nano-scaled lines, on one side of the multiplexing device to other conducting lines, such as micro-scaled lines, on the opposite side of the multiplexing device; 
         FIG. 6  is a schematic illustration of another embodiment of the multiplexing device of the previous figures, wherein the scannable conducting channel is curvilinearly (non-linearly) controlled, to connect non-coaxially (or coplanarly) disposed lines on both sides of the multiplexing device; 
         FIG. 6A  is a schematic illustration of another embodiment of the multiplexing device of  FIG. 6 , illustrating two discrete depletable regions separated by a transition region therebetween; 
         FIG. 7  is a schematic illustration of a further embodiment of the multiplexing device of the previous figures, wherein the scanning region is formed of a plurality of discrete regions; 
         FIG. 7A  is a schematic illustration of a further embodiment of the multiplexing device of  FIG. 7 , showing alternative embodiments of the discrete regions; 
         FIG. 8  is a schematic illustration of still another embodiment of the present invention, exemplifying a three-dimensional configuration comprised of a plurality of stackable multiplexing devices; 
         FIG. 9  is a block diagram illustrating a serial connectivity of a plurality of multiplexing devices of the previous figures; 
         FIG. 10  is a perspective view of an exemplary multi-node cross-point array configuration using a plurality of multiplexing devices of the previous figures, illustrating a two-dimensional architecture; 
         FIG. 11  is a schematic illustration of another exemplary multiplexing device of the present invention that is similar to the multiplexing device of  FIG. 1 , where the depletion region is controlled by a single electrode; 
         FIG. 12  is a schematic illustration of the multiplexing device of  FIG. 11 , wherein the scannable conducting channel connects conducting lines, such as nano-scaled lines, on one side of the multiplexing device to electrodes on the opposite side of the multiplexing device; 
         FIG. 13  is a schematic illustration of the multiplexing device of  FIG. 1 , where the depletion region is controlled by applying a reverse bias to a p-n (or p+-n or n+-p junction); 
         FIG. 14  is a schematic illustration of another embodiment of the multiplexing device of  FIG. 7A , showing alternative embodiments of the intermediate regions; 
         FIG. 15  is a schematic illustration of a semiconductor-on-insulator (e.g., SOI) MOSFET that shows the effects of a floating polysilicon region in the multiplexing device of  FIG. 14 ; 
         FIG. 16  is an isometric, schematic illustration of the multiplexing device of  FIG. 14 , rotated about its side; and 
         FIG. 17  is an isometric view of a multiplexing array formed of an array of multiplexing devices of  FIG. 16 . 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIGS. 1 and 2  illustrate an exemplary multiplexing device  100  of the present invention. The multiplexing device  100  comprises a conducting channel  110  that is controllably scannable within a scanning region  106 . A first gate oxide layer  104  is disposed intermediate the scanning region  106  and a first control gate  102 , at one end of the multiplexing device  100 . At the opposite end of the multiplexing device  100 , a second gate oxide layer  114  is disposed intermediate the scanning region  106  and a second control gate  116 . 
     When suitably biased by a potential V 1 , the first control gate  102  generates a first depletion region  108  in the scanning region  106 . Similarly, when the second control gate  116  is suitably biased by a potential V 2 , it generates a second depletion region  112  in the scanning region  106 . The first and second depletion regions  108 ,  112  interact to generate the conducting channel  110 . 
     The width w 1  of the first depletion region  108  is regulated by the potential V 1  and the doping concentration in the scanning region  106 . Similarly, the width w 2  of the second depletion region  112  is regulated by the potential V 2  and the doping concentration in the scanning region  106 . As a result, the width and the position of the conducting channel  110  can be very precisely controlled.  FIGS. 1 and 2  illustrate the conducting channel  110  at two different positions along the scanning region  106 , and having different widths. 
     In a structure that is suitable for the formation of multiplexing device  100 , the first and second control gates  102  and  116 , respectively, are formed of conductive layers. As used herein a conductive layer can be formed of any suitable conductive or semiconductive material. For example the conductive layer can be formed of copper, tungsten, aluminum, a silicided layer, a salicided layer, a semiconductive layer, or a conductive layer, such as metallic materials, polysilicon, silicon germanium, metallic composites, refractory metals, conductive composite materials, epitaxial regions, amorphous silicon, titanium nitride, or like conductive materials. Preferably, the conductive layers are formed of polysilicon layers that are doped with dopant atoms. Dopant atoms can be, for example, arsenic and/or phosphorus atoms for n-type material, or boron atoms for p-type material. 
     Although the first and second control gates  102  and  116  can be lithographically defined into two distinct sections that are oppositely disposed relative to the scanning region  106 , as illustrated in  FIG. 1 , it should be clear that the first and second control gates  102  and  116  could be disposed at different positions relative to the scanning region  106 . In particular, while the multiplexing device  100  is illustrated as having a generally rectangular shape, it should be clear that multiplexing device  100  could assume various other shapes, such as circular, oval, square, and various other shapes. Some of these alternative designs for the multiplexing device  100  could require the allocation of the first and second control gates  102  and  116  at various positions that are not necessarily opposite. 
     The two distinct sections of the first and second control gates  102  and  116  can be of a different conductivity type, for example: one section can be n-type while the other section can be p-type dopants or the two regions could have different metals. Known or available masking and ion implanting techniques can be used to alter the doping of portions of conductive layers. 
     The first and second control gates  102  and  116  can have the same or different widths. The width of each control gate can, for example, exceed 1000 angstroms. The voltages V 1  and V 2  applied to the first and second control gates  102  and  116 , respectively, can vary between approximately 0 and +/−100 volts. 
     A dielectric first gate oxide layer  104  is formed intermediate the first control gate  102  and the scanning region  106 . Similarly, a dielectric second gate oxide layer  114  is formed intermediate the second control gate  116  and the scanning region  106 . As used herein a dielectric layer can be any insulator such as wet or dry silicon dioxide (SiO 2 ), hafnium oxide, silicon nitride, tetraethylorthosilicate (TEOS) based oxides, borophospho-silicate-glass (BPSG), phospho-silicate-glass (PSG), boro-silicate-glass (BSG), oxide-nitride-oxide (ONO), oxynitride materials, plasma enhanced silicon nitride (p-SiN x ), a spin on glass (SOG), titanium oxide, or like dielectric materials or composite dielectric films with a high k gate dielectric. A preferred dielectric material is silicon dioxide. 
     The scanning region  106  can be formed of any suitable, depletable material. In this exemplary illustration, the scanning region  106  is formed of a depletion region, such as silicon or polysilicon layer that is lightly doped with either an n-type dopant, or a p-type dopant. In this exemplary embodiment, the scanning region  106  is doped with an n-type dopant. The width of the scanning region  106  could exceed 5 nm. The various components of regions and layers of the multiplexing devices described herein, could be made using, for example, known or available methods, such as, for example, lithographic processes. 
     In operation, by varying the voltages V 1  and V 2  on the first and second control gates  102 ,  116 , respectively, the conducting channel  110  is controllably scanned along the directions of the scanning arrows A and B, up and down the central column of the multiplexing device  100 . In the present exemplary embodiment, the width, w (e.g., w1, w2) of the depletion regions  108 ,  112  is determined by the following equation:
 
 w =(2) 1/2 λ n ( v   l ) 1/2  
 
where λ n  is the extrinsic Debye length of the conducting channel  110 ; v l  is defined by (q*(V bi +V)/kT)−2 where V bi  is the built-in potential and V is the applied voltage. For an n-concentration of 10**16/cc the maximum depletion width is on the order of 1 micron.
 
       FIG. 2  is a schematic illustration of the multiplexing device of  FIG. 1 , showing the scannable conducting channel  110  with a relatively wider width, in a second position within the scanning region  106 . 
       FIG. 3  illustrates another multiplexing device  200  according to an alternative embodiment of the present invention, wherein the scannable conducting channel  110  connects conducting lines  201 , such as nano-scaled lines  202  through  210  (e.g., having a width between approximately 5 angstroms and 1,000 angstroms), on one side of the multiplexing device  200 , to one or more electrodes  228  on the opposite side of the multiplexing device  200 . To this end, the multiplexing device  200  further includes a source  226 , a first oxide layer  222 , and a second oxide layer  224 . 
     In this exemplary embodiment, the first oxide layer  222  is in contact with the first control gate  102  and the first gate oxide layer  104 . Similarly, the second oxide layer  224  is in contact with the second control gate  116  and the second gate oxide layer  114 . The source  226  is formed intermediate the first oxide layer  222  and the second oxide layer  224 , in contact with the scanning region  106 , and the electrode  228 . Layers  222  and  224  serve to isolate the gate regions  102  and  116  from the electrode ( 228 ) and source ( 226 ). 
     The source  226  can be formed of a silicon or polysilicon layer that is doped with either an n-type dopant, or a p-type dopant. The source  226  could be formed of any conductive or semiconductive material that forms an electrical contact to the scanning region  106  and electrode  228 . In this exemplary embodiment, the source  226  is doped with an n+-type dopant. In operation, the conducting channel  110  is generated as explained earlier in connection with  FIGS. 1 and 2 , and is scanned across the scanning region  106  to establish contact with the desired line, for example line  204 , allowing the source  226  to inject electrons through the conducting channel  110 , into the selected line  204 . 
     In  FIG. 3 , the source  226  has an inner surface  236  that is illustrated as being generally flush with the oxide layers  222 ,  224 . It should however be understood that the inner surface  236 A of the source  226  could alternatively be recessed relative to the oxide layers  222 ,  224 , as shown in a dashed line. Alternatively, the inner surface  236 B of the source  226  could extend beyond the oxide layers  222 ,  224 , as shown in a dashed line. 
       FIG. 4  illustrates another multiplexing device  300  according to the present invention. Multiplexing device  300  is generally similar in construction to the multiplexing device  200  of  FIG. 3 , but is designed for a different application. The scannable conducting channel  110  of the multiplexing device  300  connects conducting lines  201 , such as nano-scaled lines  202 - 210 , on one side of the multiplexing device  300 , to other conducting lines  301 , such as nano-scaled lines  302 - 310 , on the opposite side of the multiplexing device  300 . 
     In this exemplary embodiment, the lines  301  are coaxially aligned with the lines  201 , so that the conducting channel  110  interconnects two aligned lines, such as lines  204  and  304 . 
       FIG. 5  illustrates another multiplexing device  400  according to the present invention. Multiplexing device  400  is generally similar in construction to the multiplexing device  300  of  FIG. 4 , but is designed for a different application. The scannable conducting channel  110  connects conducting lines  401 , such as nano-scaled lines  402 - 405 , on one side of the multiplexing device  400  to other conducting lines  411 , such as micro-scaled lines  412 - 415 , on the opposite side of the device  400  (e.g., having a width that exceeds approximately 100 angstroms). 
       FIG. 6  illustrates another multiplexing device  500  according to the present invention. Multiplexing device  500  is generally similar in construction to the multiplexing devices  100 ,  200 , and  300  of  FIGS. 1-3 , but will be described, for simplicity of illustration, in connection with the design of multiplexing device  300  of  FIG. 4 . The scannable conducting channel  510  is curvilinearly (non-linearly) controlled, to connect non-coaxially (or coplanarly) disposed lines  201 ,  301  on both sides of the multiplexing device  500 . 
     In order to effect this curvilinear conducting channel  510 , the multiplexing device  500  is provided with four control gates  502 ,  503 ,  504 ,  505  that are arranged in pairs, on opposite sides of the scanning region  106 . In this specific example, the control gates  502 ,  504  are disposed, adjacent to each other, on one side of the scanning region  106 , and are separated by an insulation layer  512 . Similarly, the control gates  503 ,  505  are disposed, adjacent to each other, on the opposite side of the scanning region  106 , and are separated by an insulation layer  514 . 
     Potentials can be applied independently to the control gates  502 - 505 , to generate a first depletion region  508  and a second depletion region  512 , so that the conducting channel  510  is curvilinear. To this end, control gates  502  and  503  are paired, so that when a potential V 1  is applied to the control gate  502  and a potential V 2  is applied to the control gate  503 , a first portion  520  of the conducting channel  510  is formed. Similarly, when a potential V′ 1  is applied to the control gate  504  and a potential V′ 2  is applied to the control gate  505 , a second portion  522  of the conducting channel  510  is formed. 
     Portions  520  and  522  of the conducting channel  510  are not necessarily co-linear, and are interconnected by an intermediate curvilinear section  524 . As a result, it is now possible to connect line  207  to line  305  even though these two lines are not co-linearly disposed. Other lines on opposite (or different) sides of the multiplexing device  500  could be interconnected by the conducting channel  510 , by independently scanning the first and second portions  520 ,  522  of the conducting channel  510 , along the arrows (A, B) and (C, D), respectively. 
     While  FIG. 6  illustrates only four control gates  502 - 505 , it should be clear that more than four gates can alternatively be used. 
       FIG. 6A  illustrates another multiplexing device  550  according to the present invention. Multiplexing device  550  is generally similar in construction to the multiplexing device  500  of  FIG. 6 . Similarly to  FIG. 6 , the scannable conducting channel  510  is curvilinearly (non-linearly) controlled, to connect non-coaxially (or coplanarly) disposed lines  201 ,  301  on both sides of the multiplexing device  550 . However, the switching device  550  comprises two discrete depletion regions  551 ,  552  that are separated by an intermediate, electrically conducting transition region  555 . 
     In order to effect the curvilinear conducting channel  510 , the multiplexing device  500  is provided with four control gates  562 ,  563 ,  564 ,  565  that are arranged in pairs, on opposite sides of the scanning regions  551 ,  552 , wherein each pair of control gates is separated from the other pair by the intermediate transition region  555 . In this specific example, the control gates  562 ,  564  are disposed, adjacent to each other, and are separated by the intermediate transition region  555 , while the control gates  563 ,  565  are disposed, adjacent to each other, on the opposite side of switching device  550 , and are separated by the intermediate transition region  555 . 
     Potentials can be applied independently to the control gates  562 - 565 , to generate the first depletion region  551  and the second depletion region  552 , so that the conducting channel  510  is curvilinear. To this end, control gates  562  and  563  are paired, so that when a potential V 1  is applied to the control gate  562  and a potential V 2  is applied to the control gate  563 , a first portion  520  of the conducting channel  510  is formed. Similarly, when a potential V′ 1  is applied to the control gate  564  and a potential V′ 2  is applied to the control gate  565 , a second portion  522  of the conducting channel  510  is formed. 
     The switching device  550  further includes a plurality of gate oxide layers  572 ,  573 ,  574 , and  575  that separate the control gates  562 ,  563 ,  564 , and  565  from their respective depletion regions  551 ,  552 . 
     While  FIG. 6A  illustrates four control gates  562 - 565  and one the intermediate transition region  555 , it should be clear that more than four gates and one intermediate transition region  555  can be successively used to form the switching device  550 . 
       FIG. 7  illustrates yet another multiplexing device  600  according to the present invention. Multiplexing device  600  is generally similar in construction to any of the previous multiplexing devices of  FIGS. 1-6 , but will be described, for simplicity of illustration, in connection with the design of multiplexing device  200  of  FIG. 3 .  FIG. 7  illustrates the feature that the scanning region  616  could be continuous or formed of a plurality of discrete sub-regions, such as sub-regions  606 ,  608 ,  610  with boundaries  607 ,  609  therebetween. 
       FIG. 7A  illustrates a further multiplexing device  650  according to the present invention. Multiplexing device  650  is generally similar in construction to multiplexing device  600  of  FIG. 7 . The scanning region  656  of multiplexing device  600  is formed of a plurality of discrete sub-regions, such as sub-regions  676 ,  677 ,  678 , with intermediate regions  680 ,  681 ,  682  therebetween. The intermediate regions  680 ,  681 ,  682  serve the function of extending the depletion regions  676 ,  677 ,  678  and further isolating the conducting channels from each other. 
     While only three intermediate regions  680 ,  681 ,  682  are illustrated, it should be clear that one or more intermediate regions may be formed. In this particular embodiment, the intermediate regions  680 ,  681 ,  682  are generally similar in design and construction, and are dispersed along the scanning region  656 . In another embodiment, the intermediate regions  681 ,  682  are disposed contiguously to each other. The spacing between the intermediate regions  680 ,  681 ,  682  and the widths of all the regions in the embodiments described herein, could be changed to suit the particular applications for which the multiplexing devices are designed. 
     Considering now an exemplary intermediate region  681 , it is formed of two semiconductor layers  690 ,  691  with an intermediate layer  692  having a high dielectric constant material that is sandwiched between the semiconductor layers  690 ,  691 . According to another embodiment, the intermediate layer  692  is made of a semiconducting material that is different from that of layers  690  and  691  to form a quantum well structure. 
     Intermediate region  682  includes an intermediate region  699  that is generally similar to the intermediate region  692 . Alternatively, the intermediate regions  692 ,  699  could have different work functions than the work function of semiconductor layer  691  so as to produce a quantum well function. 
       FIG. 8  illustrates another multiplexing device  700  of the present invention, exemplifying a three-dimensional configuration. Multiplexing device  700  is comprised of a plurality of stackable multiplexing devices, such as multiplexing devices  100 ,  200 ,  300 ,  400 ,  500 ,  600 , that can be different or similar. Each of these stackable multiplexing devices can be independently controlled as described in connection with  FIGS. 1-7 . 
     According to this embodiment, one, or a group of multiplexing devices  100 ,  200 ,  300 ,  400 ,  500 ,  600  can be selected by applying suitable depletion potentials V 3 , V 4 , to two outer electrodes  703 ,  704 , respectively. Once the multiplexing device or a group of multiplexing devices  100 ,  200 ,  300 ,  400 ,  500 ,  600  is selected, the selected multiplexing device or a group of multiplexing devices  100 ,  200 ,  300 ,  400 ,  500 ,  600  is operated individually, as described earlier. In addition, a high-K insulation layer (e.g.,  711 ,  712 ,  713 ,  714 ,  715 ) is interposed between two contiguous multiplexing devices (e.g.,  100 ,  200 ,  300 ,  400 ,  500 ,  600 ). 
       FIG. 9  illustrates another multiplexing device  800  of the present invention, exemplifying the serial connectivity of a plurality of multiplexing devices, such as multiplexing devices  200 ,  300 ,  400 . Each of these serially connected multiplexing devices  200 ,  300 ,  400  can be independently controlled, and the output of one multiplexing device used to control the accessibility of the subsequent multiplexing device. 
       FIG. 10  is a perspective view of an exemplary multi-node cross-point array  900  using at least two multiplexing device, e.g.,  200 ,  300  whose respective outputs are selected as described above, onto output lines  201 ,  301 , are selected as described above. The selected outputs are processed (collectively referred to as “processed outputs”), as desired, by for example, operational devices  950 . The processed outputs can be used directly, or, as illustrated in  FIG. 10 , they can be further fed to one or more multiplexing devices, e.g.,  400 ,  700 , resulting in outputs that are fed to respective output lines  400 ,  700 . 
     The operational devices  950  could be, for example, memory cells, logic devices, current-driven or voltage-driven elements, such as light emitters, heat emitters, acoustic emitters, or any other device that requires addressing or selective accessibility. 
     As an example, the operational device  950  can include a switchable element that is responsive to current change or voltage change, or phase change, resulting in change of resistance or magneto-resistance, thermal conductivity or change in electrical polarization. Alternatively, the operational devices can include a carbon nano tube, a cantilever, a resonance driven device, or a chemical or biological sensor. 
       FIG. 11  is a schematic illustration of another exemplary multiplexing device  1100  according to the present invention. The multiplexing device  1100  is generally similar in design and operation to the multiplexing device  100  of  FIG. 1 , and comprises a conducting region  1112  that is controllably scannable within a scanning region  106 . The gate oxide layer  104  is disposed intermediate the scanning region  106  and the control gate  102 , at one end of the multiplexing device  1100 . At the opposite end of the multiplexing device  1100 , an insulator layer, such as an oxide layer  1114 , is disposed contiguously to the scanning region  106 . It should be clear that the insulator layer  1114  is optional. 
     The depletion region  1108  is controlled by applying a potential V 1  to the control gate  102 , in order to generate the conducting region  1112 . An important feature of the multiplexing device  1100  is to control the width w of the depletion region  1108  using a single control gate  102 . Unlike the multiplexing device  100 , the undepleted region  1112  of the multiplexing device  1100  is not necessarily a small region. It could, in some cases, encompass the entire scanning region  106  under the control gate  102  and the gate oxide  104 . As further illustrated in  FIG. 12 , the multiplexing device  1100  enables concurrent multibit sequential programming. 
       FIG. 12  is a schematic illustration of the multiplexing device  1100  of  FIG. 11 , wherein the scannable conducting channel  110  connects conducting lines, such as nano-scaled lines  201 , on one side of the multiplexing device  1100  to electrodes (or to a micro line) on the opposite side of the multiplexing device  1100 . Since the multiplexing device  1100  comprises a single control gate (or electrode)  102 , many nano-scaled lines  201  could be selected for any value of the control gate potential V 1 . This requires a serial access scheme as compared to a random access scheme used by the embodiments of  FIGS. 1-8 . 
       FIG. 13  is a schematic illustration of a multiplexing device  1300  that is similar to the multiplexing device  100  of  FIG. 1 , but without the two gate oxide layers  104 ,  114 . In the previous embodiments, the depletion regions  108 ,  112  were comprised, for example of a depletion region of a Metal Oxide Semiconductor (MOS) system. However, the depletion regions  108 ,  112  of the multiplexing device  1300  of  FIG. 13  form two p+-n junctions (or alternatively one p+-n junction) with the adjacent control gates  102 ,  116 , respectively. In an alternative embodiment, the depletion regions  108 ,  112  form two n+-p junctions (or alternatively one n+-p junction) with the adjacent control gates  102 ,  116 , respectively. 
     By applying potentials V 1  and V 2  to the p+ regions (control gates  102  and  116 ), a conduction channel  110  could be formed in around the middle of the scanning region  106 . One of the advantages of this multiplexing device  1300  is that the breakdown voltages of p-n junctions can be higher than the gate oxide breakdown voltages. This means that higher voltages could be applied to the control gate  102 ,  116 . This could also mean that the scanning region  106  could be bigger. In an alternative embodiment, the multiplexing device  1300  could be formed of a single control gate, such as control gate  102 . 
     In yet another embodiment, the depletion regions  108 ,  112  of the multiplexing device  1300  are formed by Schottky barriers (Metal—semiconductor regions), wherein the first and second control gates  102  and  116  are formed of a metal material. The depletion width in the Schottky barrier is controlled much the same way as the depletion width in a p-n junction. 
     Similarly to the illustration of  FIG. 3 , it is possible to select nano-scaled lines  201  by applying appropriate potentials V 1  and V 2  to the first and second control gates  102 , 116 , respectively, and connect it to the micro-scaled line or source  226 . Alternatively Schottky barriers (metal-n or metal-p) regions may be used to do the connection as well. 
       FIG. 14  is a schematic illustration of another multiplexing device  1400  according to the present invention. The multiplexing device  1400  is generally similar in function and operation to the multiplexing device  650  of  FIG. 7A , and shows an alternative embodiment of the intermediate regions  1480 ,  1481 , in order to illustrate an exemplary instance of nano-pillar addressing. 
     In this embodiment, the semiconducting depletion regions  676 ,  677 ,  678  are physically separated through a combination of dielectrics (e.g., oxide/nitride/high-K) and electrode/semiconducting regions that are referred to as intermediate regions  1480 ,  1481 . This allows a reduction in the leakage between the bits and extends the range of the maximum depletion region possible. This may also allow low voltage operation. Though only three semiconducting depletion regions  676 ,  677 ,  678  and two intermediate regions  1480 ,  1481  are shown for illustration purpose only, it should be clear that a different number of regions could alternatively be used. 
     Each semiconductor depletion region  676 ,  677 ,  678  is bounded by at least one thin dielectric layer, e.g.,  690 ,  691 , which is preferably but not necessarily composed of an oxide in order to passivate the sidewalls and to guarantee good electrical properties. Sandwiched between layers  690  and  691  in each intermediate region  1480 ,  1481  is a high-K dielectric material  1491 ,  1492 , respectively. This minimizes the voltage drop between the intermediate regions  1480 ,  1481  while maintaining isolation. The high-K dielectric material  1492  could be any dielectric with a reasonable dielectric constant, wherein a higher dielectric constant provides better electrical properties. 
     Each of the intermediate regions  1480 ,  1481  further comprises two side insulation regions on opposite ends of the high-K dielectric material  1491 ,  1492 . More specifically, intermediate region  1480  further comprises two side insulation regions  693 ,  695 , and intermediate region  1481  further comprises two side insulation regions  694 ,  696 . Side insulation regions  693 - 696  isolate the high-K dielectric material  1491 ,  1492  from the semiconducting depletion regions  676 ,  677 ,  678 . 
     Alternatively, each of the dielectric layers  690 ,  691  comprises a thin dielectric material, typically oxide, that bounds the semiconducting depletion regions  676 ,  677 ,  678 . However, the intermediate regions  1480 ,  1481  between the dielectric layers  690 ,  691  are filled with a semiconducting material or a metal material to form regions  1491 ,  1492 . Each of the regions  1491 ,  1492  is preferably floating and its potential depends on the capacitive coupling of the different control electrodes  102 , 114  to these regions  1491 ,  1492 . 
     This design is desirable for the following reasons. A heavily doped semiconductor or metallic region further minimizes the applied voltage requirements. In addition, the work function difference between the electrode/semiconductor region  1492  and the semiconductor region results in an inversion layer (thin layer of electrons) at the interface of the semiconducting depletion regions  676 ,  677 ,  678 . This allows the multiplexing device  1400  to work via the depletion of the inversion layer charge as opposed to a charge resulting from ionized dopant atoms, and therefore minimizes dopant fluctuation effects. In this case, insulation regions  693 - 696  are required to prevent shorting of the electrodes (i.e.,  1491 ,  1492 ) to the various semiconducting depletion regions  676 ,  677 ,  678  and to keep it electrically isolated. This effect is further illustrated in  FIG. 15  using the example of a simple MOS device  1500 . 
     As further illustrated in  FIG. 7A , the multiplexing device  1400  of  FIG. 14 , wherein the scannable conducting channel  110  could be connected to conducting lines, such as nano-scaled lines  201 , on one side of the multiplexing device  1400  to electrodes (or micro lines) on the opposite side of the multiplexing device  1400 . 
       FIG. 15  illustrates the effect of including floating polysilicon/electrode regions ( 1491  and  1492  in  FIG. 14  or  1525  in  FIG. 15 ) in semiconducting structure  1500 . Structure  1500  is generally formed of a silicon on insulator (SOI) wafer with a thin (e.g., less than approximately 100 nm) silicon region on top of an insulator (oxide). The MOS device includes an n-channel device with n+ source regions  1505  and drain regions  1510 . The gate  1525  is formed of n+ polysilicon material. At zero bias gate, the potentials of the source  1505  and drain  1510  develop an inversion layer  1507  in the channel of semiconductor region  1515 . This inversion layer  1507  is generated because of the work function difference between the gate  1525  and the silicon/semiconductor  1515 . This work function difference causes the bands in the silicon  1515  at zero gate voltage to bend in much the same way as a transistor with positive applied bias. This inversion charge in the addressing scheme may be depleted in much the same way as dopant charge. One way to think about the transistor in  FIG. 15  is that it emulates a negative threshold voltage transistor. 
     Referring now to  FIG. 16 , it illustrates a multiplexing device  1600  according to the present invention. Multiplexing device  1600  is generally similar to multiplexing device  1400  of  FIG. 14 , but is rotated about its side. Multiplexing device  1600  comprises a plurality of nano-pillars  1676 ,  1677 ,  1678 ,  1679  that are interposed between the first control gate  102 , the second control gate  116 , and intermediate regions  1610 ,  1615 ,  1620 . The intermediate regions  1610 ,  1615 ,  1620  are generally similar in construction and operation to the intermediate regions  1480 ,  1481  of  FIG. 14 . While four nano-pillars  1676 ,  1677 ,  1678 ,  1679  are illustrated, it should be clear that a different number of nano-pillars can be selected. A plurality of oxide/dielectric layers  1686 ,  1687 ,  1688  surround the intermediate regions  1610 ,  1615 ,  1620  to isolate them from the nano-pillars  1676 ,  1677 ,  1678 ,  1679 , and the operational devices  1635 ,  1645 . 
     Arrows C indicate the direction of the electrical currents flowing through one or more nano-pillars  1676 ,  1677 ,  1678 ,  1679  selected by depletion, as described earlier. While the direction of the current is shown in the current direction, it should be clear that the current could alternatively flow in the opposite direction. The current flows between the two electrodes  1602 ,  1604 , through operational devices  1635 ,  1645  (denoted earlier as operational devices  950 ). 
       FIG. 17  shows a multiplexing array  1700  that is formed of an array of multiplexing devices  1600  of  FIG. 16 , with the electrodes  1602 ,  1604 , the operational devices  1635 ,  1645 , and the control gates  102 ,  116  removed for clarity of illustration. The plurality of multiplexing devices  1600  are separated and insulated by a plurality of insulation layers  1705 . The insulation layers  1705  are preferably, but not necessarily formed of oxide layers, and could alternatively be made of the same material as the intermediate region  1610 . While only four multiplexing devices  1600  are illustrated, it should be clear that a different number of multiplexing devices  1600  can alternatively be used. 
     It is to be understood that the specific embodiments of the present invention that have been described are merely illustrative of certain applications of the principle of the multiplexing device. Numerous modifications may be made to the multiplexing device without departing from the spirit and scope of the present invention.

Technology Classification (CPC): 8