Patent Publication Number: US-6657913-B2

Title: Array organization for high-performance memory devices

Description:
RELATED APPLICATION 
     This application is a divisional of U.S. patent application Ser. No. 09/628,145 filed Jul. 28, 2000 and commonly assigned, now U.S. Pat. No. 6,396,728 issued May 28, 2002, the entire contents of which are incorporated by reference herein. 
    
    
     TECHNICAL FIELD OF THE INVENTION 
     The present invention relates generally to semiconductor memory devices, and in particular, the present invention relates to organization of memory arrays for global bit-line architecture in high-performance semiconductor memory devices. 
     BACKGROUND OF THE INVENTION 
     Memory devices are typically provided as internal storage areas in the computer. The term memory identifies data storage that comes in the form of integrated circuit chips. In general, memory devices contain an array of memory cells for storing data, and row and column decoder circuits coupled to the array of memory cells for accessing the array of memory cells in response to an external address. 
     There are several different types of memory. One type is RAM (random-access memory). This is typically used as main memory in a computer environment. RAM refers to read and write memory; that is, you can repeatedly write data into RAM and read data from RAM. This is in contrast to ROM (read-only memory), which generally only permits the user in routine operation to read data already stored on the ROM. Most RAM is volatile, which means that it requires a steady flow of electricity to maintain its contents. As soon as the power is turned off, whatever data was in RAM is lost. 
     Computers almost always contain a small amount of ROM that holds instructions for starting up the computer. Unlike RAM, ROM generally cannot be written to in routine operation. An EEPROM (electrically erasable programmable read-only memory) is a special type of non-volatile ROM that can be erased by exposing it to an electrical charge. Like other types of ROM, EEPROM is traditionally not as fast as RAM. EEPROM comprise a large number of memory cells having electrically isolated gates (floating gates). Data is stored in the memory cells in the form of charge on the floating gates. Charge is transported to or removed from the floating gates by programming and erase operations, respectively. 
     Yet another type of non-volatile memory is a Flash memory. A Flash memory is a type of EEPROM that can be erased and reprogrammed in blocks instead of one byte at a time. Many modern PCs have their BIOS stored on a flash memory chip so that it can easily be updated if necessary. Such a BIOS is sometimes called a flash BIOS. Flash memory is also popular in modems because it enables the modem manufacturer to support new protocols as they become standardized. 
     A typical Flash memory comprises a memory array that includes a large number of memory cells arranged in row and column fashion. Each of the memory cells includes a floating gate field-effect transistor capable of holding a charge. The cells are usually grouped into blocks. Each of the cells within a block can be electrically programmed in a random basis by charging the floating gate. The charge can be removed from the floating gate by a block erase operation. The data in a cell is determined by the presence or absence of the charge in the floating gate. 
     A synchronous DRAM (SDRAM) is a type of DRAM that can run at much higher clock speeds than conventional DRAM memory. SDRAM synchronizes itself with a CPU&#39;s bus and is capable of running at 100 MHZ, about three times faster than conventional FPM (Fast Page Mode) RAM, and about twice as fast EDO (Extended Data Output) DRAM and BEDO (Burst Extended Data Output) DRAM. SDRAMs can be accessed quickly, but are volatile. Many computer systems are designed to operate using SDRAM, but would benefit from non-volatile memory. 
     As memory sizes continue to increase, satisfying the demands for high-speed access of memory arrays becomes increasingly difficult. Increasing memory sizes have been made possible in large part by continuing advances in semiconductor fabrication, i.e., placing more transistors and interconnect lines in the same die area. However, reduced dimensions of transistors leads to lower drive while reduced dimensions of interconnect lines leads to increased resistance. Managing this reduced drive and higher resistance through array organization thus becomes an important factor in providing high-speed access in high-performance memory devices. 
     For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for alternate array architectures for high-performance memory devices. 
     SUMMARY OF THE INVENTION 
     The above-mentioned problems with memory devices and other problems are addressed by the present invention and will be understood by reading and studying the following specification. 
     Various embodiments of the invention have architectures suited for high-performance memory devices, with particular reference to synchronous non-volatile memory devices. Memory devices in accordance with the various embodiments of the invention include blocks of memory cells arranged in columns with each column of memory cells coupled to a main bit line. Such memory devices further include sector bit lines having multiple main bit lines coupled to each sector bit line through selective coupling devices with each sector bit line extending to main bit lines in each memory block of a memory sector. Sector bit lines are coupled to sensing devices and the output of each sensing device is coupled to a global bit line through a selective coupling device, with each global bit line coupled to more than one sensing device through the selective coupling devices. For embodiments having multiple sectors, the global bit lines may extend to more than one sector. The global bit lines are multiplexed and input to helper flip-flops for output to the data output registers of the memory device. This array organization permits tight packing of individual memory cells with high-speed access capabilities. 
     For one embodiment, the invention provides a memory array. The memory array includes a first memory block having columns of memory cells coupled to main bit lines of the first memory block, a second memory block having columns of memory cells coupled to main bit lines of the second memory block, sector bit lines coupled to main bit lines in both memory blocks, sensing devices coupled to the sector bit lines, and at least one global bit line selectively coupled to the sensing devices. Each sector bit line is selectively coupled to at least two main bit lines of each memory block. 
     For another embodiment, the invention provides a memory bank. The memory bank includes a first number of memory sectors each having a second number of memory blocks, each memory block having a third number of columns of non-volatile memory cells with each column of non-volatile memory cells coupled to a main bit line. The memory bank further includes a fourth number of sector bit lines in each memory sector, wherein each sector bit line extends to each memory block in its associated memory sector and wherein the fourth number is one-half the third number. The memory bank still further includes a plurality of block pass transistors, wherein one block pass transistor is coupled between each main bit line and a sector bit line to selectively couple each main bit line to a sector bit line, and wherein each main bit line is selectively coupled to only one sector bit line and each sector bit line is selectively coupled to two main bit lines in each memory block. The memory bank still further includes a plurality of sense amplifiers in each memory sector, wherein each sense amplifier is coupled to two sector bit lines in its associated memory sector, and a plurality of global bit lines, wherein each output of a sense amplifier is coupled to only one global bit line through a selective coupling device and each global bit line is coupled to an output of more than one sense amplifier in each memory sector of the memory bank through selective coupling devices. 
     For still another embodiment, the invention provides a memory array. The memory array includes at least one memory bank, each memory bank having at least one memory sector. Each memory sector includes at least two memory blocks, each memory block having columns of non-volatile memory cells coupled to a plurality of main bit lines and a plurality of sector bit lines, wherein each sector bit line extends to each memory block of its associated memory sector. Each memory sector further includes a plurality of block pass transistors coupled between each plurality of main bit lines and the plurality of sector bit lines to selectively couple each main bit line to a sector bit line, wherein each main bit line is selectively coupled to only one sector bit line of its associated memory sector and each sector bit line is selectively coupled to more than one main bit line of its associated memory sector. Each memory sector still further includes a plurality of sense amplifiers coupled to the plurality of sector bit lines, wherein each sense amplifier is coupled to two sector bit lines of its associated memory sector, and a plurality of global bit lines, wherein an output of each sense amplifier is selectively coupled to only one global bit line and each global bit line is selectively coupled to an output of more than one sense amplifier of each memory sector of its associated memory bank. 
     For a further embodiment, the invention provides a synchronous flash memory device. The memory device includes a plurality of memory banks containing non-volatile flash memory cells and a command execution logic coupled to the plurality of memory banks for receiving at least a system clock input signal and for generating commands to control operations performed on the plurality of memory banks for synchronization to a system clock. Each memory bank includes a first number of memory sectors each having a second number of memory blocks, with each memory block having a third number of columns of non-volatile flash memory cells where each column of non-volatile flash memory cells is coupled to a main bit line. Each memory bank further includes a fourth number of sector bit lines in each memory sector, wherein each sector bit line extends to each memory block in its associated memory sector and wherein the fourth number is one-half the third number. Each sector bit line is selectively coupled to two main bit lines in each memory block while each main bit line is selectively coupled to only one sector bit line. Each memory bank further includes a plurality of sense amplifiers in each memory sector, wherein each sense amplifier is coupled to two sector bit lines in its associated memory sector, and a plurality of global bit lines, wherein an output of each sense amplifier is selectively coupled to only one global bit line and each global bit line is selectively coupled to an output of more than one sense amplifier in each memory sector of the memory bank. 
     The invention further provides methods and apparatus of varying scope. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram of a memory device in accordance with the invention. 
     FIG. 2A is a top view of a memory assembly showing a package pin assignment diagram in accordance with the invention. 
     FIG. 2B is a top view of a memory assembly showing a package bump assignment diagram in accordance with the invention. 
     FIG. 3 is a schematic of a portion of a memory block in accordance with one embodiment of the invention. 
     FIG. 4A is a schematic of a portion of a memory sector in accordance with one embodiment of the invention. 
     FIG. 4B is a schematic of a portion of a memory sector in accordance with another embodiment of the invention. 
     FIG. 5 is a schematic of a portion of a memory sector in accordance with a further embodiment of the invention. 
     FIG. 6 is a schematic of portions of multiple memory sectors sharing a global bit line in accordance with one embodiment of the invention. 
     FIG. 7 is a schematic of portions of multiple memory sectors sharing a global bit line in accordance with another embodiment of the invention. 
     FIG. 8 is a block diagram of a memory bank in accordance with one embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following detailed description of the present embodiments, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments in which the inventions may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that process, electrical or mechanical changes may be made without departing from the scope of the present invention. The terms wafer and substrate used in the following description include any base semiconductor structure. Both are to be understood as including silicon-on-sapphire (SOS) technology, silicon-on-insulator (SOI) technology, thin film transistor (TFT) technology, doped and undoped semiconductors, epitaxial layers of a silicon supported by a base semiconductor structure, as well as other semiconductor structures well known to one skilled in the art. Furthermore, when reference is made to a wafer or substrate in the following description, previous process steps may have been utilized to form regions/junctions in the base semiconductor structure, and terms wafer or substrate include the underlying layers containing such regions/junctions. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims and equivalents thereof. 
     FIG. 1 is a block diagram of one embodiment of a synchronous memory device in accordance with the invention. The memory device  100  includes an array of non-volatile flash memory cells  102  having an organization as described herein. All access commands to the array  102  of the memory device  100  are synchronized to a system clock input signal (CLK), thus the memory device  100  may be referred to as a synchronous flash memory device or synchronous non-volatile memory device. However, memory array organization in accordance with the various embodiments described herein is not limited to synchronous memory devices. 
     The array  102  is arranged in a plurality of addressable banks. In one embodiment, the memory contains four memory banks  104 ,  106 ,  108  and  110 . Each memory bank contains addressable sectors of memory cells. The data stored in the memory can be accessed using externally provided location addresses received by address register  112  through a plurality of address inputs  138 . The externally provided addresses may come, for example, from a processor  101  of an electronic system as is known in the art. The addresses are decoded using row address multiplexer circuitry  114 . The addresses are also decoded using bank control logic  116  and row address latch and decode circuitry  118 . To access an appropriate column of the memory, column address counter and latch circuitry  120  couples the received addresses to column decode circuitry  122 . Circuit  124  provides input/output (I/O) gating, data mask logic, read data latch circuitry and write driver circuitry. Data is input through data input registers  126  and output through data output registers  128  using a plurality of data inputs/outputs  140 . The data inputs/outputs  140  may be coupled to, for example, the processor  101  of an electronic system. Command execution logic  130  is provided to generate commands to control the basic operations performed on the memory banks of the memory device. A state machine  132  is also provided to control specific operations performed on the memory banks. A status register  134  and an identification register  136  can also be provided to output data. The command circuit  130  and/or state machine  132  can be generally referred to as control circuitry to control read, write, erase and other memory operations. As is known in the art, integrated circuit memory devices of the type described with reference to FIG. 1 may be fabricated on a substrate, such as a semiconductor wafer, and may be referred to as a memory chip. 
     FIG. 2A illustrates an interconnect pin assignment of one embodiment of the present invention as a memory assembly having a pin layout substantially similar to a standard SDRAM 54-pin TSOP (thin small-outline package) package. Accordingly, the memory assembly has a memory package  150  having 54 interconnect pins and a memory device (not shown) in accordance with the invention. The memory device is contained in the memory package  150 . The address inputs, data inputs/outputs, power inputs and clock and control signal inputs of the memory device are coupled to the interconnect pins of the memory package  150  in a conventional manner. Two interconnects shown in the embodiment of FIG.  2 A and not present in standard SDRAM packages include control signal RP# and power input VccP. Although knowledge of the function of the various clock and control signals and the various power inputs is not essential to understanding the present invention, a detailed discussion is included in U.S. patent application Ser. No. 09/567,773 filed May 10, 2000 and titled, “Flash with Consistent Latency,” which is commonly assigned. 
     FIG. 2B illustrates a bump assignment of one embodiment of the present invention as a memory assembly having a bump layout substantially similar to an industry standard SDRAM 60-bump FBGA (fine-pitch ball grid array) package. Memory package  160  is generally similar to memory package  150  except that the interconnects of memory package  160  have bump connections instead of the pin connections of memory package  150 . The present invention, therefore, is not limited to a specific package configuration. Furthermore, the invention is not limited to memory packages having pin or bump layouts substantially similar to the interconnect layout of an industry-standard SDRAM package, but is applicable to other memory packages having memory devices containing arrays having an organization in accordance with the various embodiments of the invention. 
     Arrays of non-volatile memory cells are often configured as floating gate transistors placed at the intersection of word lines and bit lines. The word lines are coupled to the control gates of the floating gate transistors. FIG. 3 is a schematic of a portion of a non-volatile memory block  300  as a portion of a memory array in accordance with one embodiment of the invention. 
     The detail of memory block  300  is provided to better understand the various embodiments of the invention. However, other memory blocks containing columns of memory cells coupled to bit lines are suited for use in the invention. Accordingly, the invention is not limited to the specific floating-gate memory cell and layout described with reference to FIG.  3 . 
     As shown in FIG. 3, the memory block  300  includes word lines  302  and intersecting main bit lines  304 . For ease of addressing in the digital environment, the number of word lines  302  and the number of bit lines  304  are each some power of two, e.g., 256 word lines  302  by 4,096 bit lines  304 . The main bit lines  304  may be selectively coupled to global bit lines in accordance with the invention, i.e., no more than one main bit line  304  may be in electrical communication with any given global bit line in normal operation, with remaining main bit lines  304  being electrically isolated from that global bit line. 
     Floating gate transistors  306  are located at each intersection of a word line  302  and a main bit line  304 . The floating gate transistors  306  represent the non-volatile memory cells for storage of data. Typical construction of such floating gate transistors  306  include a source  308  and a drain  310  constructed from an N+-type material of high impurity concentration formed in a P-type semiconductor substrate of low impurity concentration, a channel region formed between the source and drain, a floating gate  312 , and a control gate  314 . Floating gate  312  is isolated from the channel region by a tunneling dielectric and from the control gate  314  by an intergate dielectric. The materials of construction are not critical to the invention, but commonly include doped polysilicon for the gate materials, and silicon oxides, nitrides or oxynitrides for the dielectric materials. Floating gate transistors  306  having their control gates  314  coupled to a word line  302  typically share a common source  308  depicted as array source  316 . As shown in FIG. 3, floating gate transistors  306  coupled to two adjacent word lines  302  may share the same array source  316 . Floating gate transistors  306  have their drains coupled to a main bit line  304 . A column of the floating gate transistors  306  are those transistors commonly coupled to a given main bit line  304 . A row of the floating gate transistors  306  are those transistors commonly coupled to a given word line  302 . 
     The following discussion provides examples of programming, reading and erasing memory cells of the type depicted in FIG.  3 . During programming, a positive programming voltage of about 12 volts is applied to the control gate  314 . This positive programming voltage attracts electrons from the P-type substrate and causes them to accumulate at the surface of channel region. A voltage on the drain  310  is increased to about 6 volts by applying the potential to the associated main bit line  304 , and the source  308  is connected to an array ground  318  through the array source  316 . As the drain-to-source voltage increases, electrons flow from the source  308  to the drain  310  via the channel region. As electrons travel toward the drain  310 , they acquire substantially large kinetic energy and are referred to as hot electrons. 
     The voltages at the control gate  314  and the drain  310  create an electric field in the tunneling dielectric layer. This electric field attracts the hot electrons and accelerates them toward the floating gate  312 . At this point, the floating gate  312  begins to trap and accumulate the hot electrons and starts a charging process. Gradually, as the charge on the floating gate  312  increases, the electric field in the tunneling dielectric layer decreases and eventually loses it capability of attracting any more of the hot electrons to the floating gate  312 . At this point, the floating gate  312  is fully charged. The negative charge from the hot electrons collected in the floating gate  312  raises the cell&#39;s threshold voltage (Vt) above a logic 1 voltage. When a control voltage on the control gate  314  is brought to a logic 1 during a read operation, the cell will barely turn on. The control voltage is applied to a word line  302 , and thus the control gate  314 , in response to control signals received from a row decoder circuit. Sensing devices, such as sense amplifiers, are used in the memory to detect and amplify the state of the floating gate transistor  306  detected on the main bit line  304  during a read operation. The floating gate transistor  306  is coupled to a sense amplifier and the appropriate sense amplifier is coupled to a data output register through a global bit line in response to control signals received from a column decoder circuit. Thus, a memory cell is selected by a decoded address and data is read from the memory cell based upon its “on” characteristics. 
     Electrons are removed from the floating gate  314  to erase the floating gate transistor  306 . Many memories, including flash memories, use Fowler-Nordheim (FN) tunneling to erase a memory cell. The erase procedure is accomplished by electrically floating the drain  310 , grounding the source  308 , and applying a high negative voltage (e.g., −12 volts) to the control gate  314 . This creates an electric field across the tunneling dielectric layer and forces electrons off of the floating gate  312  which then tunnel through the tunneling dielectric layer. Erasures are generally carried out in blocks rather than individual cells. 
     To reduce problems associated with high resistance levels in the array source  316 , the array source  316  is regularly coupled to a metal or other highly conductive line to provide a low-resistance path to ground. The array ground  318  serves as this low-resistance path. For one embodiment, an array ground  318  is formed using a spacing of 16 columns of memory cells. The array ground  318  is generally formed in the metal  1  (M 1 ) layer of the semiconductor fabrication process and is coupled to multiple array sources  316  within the memory block  300 . 
     FIG. 4A is a schematic of a portion of a memory sector  400  in accordance with one embodiment of the invention showing the coupling of main bit lines  304  of a memory block  300  to global bit lines  426  of the memory sector  400 . The memory sector  400  includes at least one and preferably two or more memory blocks  300 . For ease of addressing, the number of memory blocks  300  included in a memory sector  400  is generally some power of two, and each memory block  300  preferably has the same number of rows and columns. In the embodiment of FIG. 4A, memory sector  400  includes two memory blocks  300   0  and  300   1  identified as main blocks MB 0  and MB 1 , respectively. Each memory block  300  has a row and column organization as generally described with reference to FIG.  3 . In the interest of clarity, individual memory cells are not shown in FIG.  4 A. To couple an individual memory cell to a sense amplifier  424 , its associated word line is activated, thus activating the target memory cell as well as other memory cells associated with the word line. Note that to simplify access circuitry, word lines may be simultaneously activated in more than one memory block  300 . The main bit line  304  associated with the target memory cell is then selectively coupled to an associated sector bit line  420  such as by using a block pass transistor  422  such that all other main bit lines  304  associated with the sector bit line  420  are electrically isolated from the sector bit line  420 . Block pass transistors  422  are activated in response to control signals from the row and column decoder circuits indicative of the target memory cell. Note that multiple main bit lines  304  may be simultaneously coupled to multiple associated sector bit lines  420  to read multiple data bits in the same read operation. Memory cells associated with main bit lines  304  not coupled to a sector bit line  420  are ignored, i.e., such memory cells are electrically isolated from a sensing device. 
     As shown in FIG. 4A, four main bit lines  304 , two from each block  300 , are coupled to each sector bit line  420  through selective coupling devices, such as block pass transistors  422 , with each sector bit line  420  extending to two or more blocks  300 . The main bit lines  304  are electrically isolated from each sector bit line  420  until actively coupled to a sector bit line  420  through their associated block pass transistors  422 . Sector bit lines  420  are coupled in pairs to the inputs of the sense amplifiers  424 . Accordingly, for the embodiment depicted in FIG. 4A, there is one sense amplifier  424  located in the span of every four main bit lines  304 . By selectively coupling each sense amplifier  424  to more than two main bit lines  304 , the memory block  300  can make use of tighter packing of memory cells and main bit lines  304 . To selectively couple each sense amplifier  424  to only two main bit lines  304 , the spacing of the main bit lines  304  may need to increase, the dimensions of the sense amplifiers  424  may need to decrease, or the sense amplifiers  424  may need to be staggered on each end of the memory sector  400 ; each case, however, would generally lead to a detrimental increase in die size or a detrimental reduction in signal drive by the sense amplifiers  424 . As shown in FIG. 4A, each sense amplifier  424  may be selectively coupled to one of eight main bit lines  304 , and thus to a memory cell in one of eight columns of memory cells, through its associated sector bit lines  420 . 
     Each output  425  of each sense amplifier  424  is coupled to a global bit line  426  through a selective coupling device, such as transistors  428 . Sense amplifiers  424  are multiplexed in response to control signals from the column decoder circuit indicative of the target memory cell to provide the output of the target sense amplifier  424 , and thus the data value of the target memory cell, on the global bit line  426 . Using the foregoing memory array organization, large memory arrays having high-speed access and reduced die area are possible. While only two main bit lines  304  from each block  300  are selectively coupled to each sector bit line  420  in FIG. 4A, additional pairs of main bit lines  304  could be coupled to each sector bit line  420  through additional block pass transistors  422 . 
     Although the sense amplifiers  424  in FIG. 4A are depicted as having a single output  425  coupled to a single global bit line  426 , the sense amplifier output  425  is often a pair of output lines, one line for providing the data value and the other line for providing the binary complement of the data value. For such embodiments, each output  425  of a sense amplifier  424  is selectively coupled to one global bit line  426  of a global bit line pair. FIG. 4B is a schematic of one embodiment of a memory sector  400  showing the coupling of two outputs  425  from each sense amplifier  424  to a global bit line  426  of a global bit line pair. For clarity, memory blocks  300 , main bit lines  304  and block pass transistors  422  are omitted in FIG.  4 B. The first output  425   a  of a sense amplifier  424  is coupled to the first bit line  426   a  of the global bit line pair and the second output  425   b  of a sense amplifier  424  is coupled to the second bit line  426   b  of the global bit line pair  427  through transistors  428 . Note that for this embodiment, the two transistors  428  selectively coupling each output of a sense amplifier  424  to a global bit line  426  are each controlled by the same control signal, and thus may be thought of as a single selective coupling device. For simplicity, subsequent figures will depict the output  425  of each sense amplifier  424  as a single output coupled to a global bit line  426 . However, as is apparent from the discussion accompanying FIG. 4B, this can represent a pair of sense amplifier outputs coupled to a global bit line pair. 
     FIG. 5 is a schematic of a portion of a memory sector  400  in accordance with another embodiment of the invention having more than two main memory blocks  300 . In FIG.  5  and subsequent figures, certain detail and reference numbers are omitted in the interest of clarity as higher levels of the memory device are described. The omitted detail is apparent from the context of use with reference to preceding figures. 
     The memory sector  400  of FIG. 5 has four memory blocks  300   0 ,  300   1 ,  300   2  and  300   3 , identified as main blocks MB 0 , MB 1 , MB 2  and MB 3 , respectively. Main bit lines  304  from each memory block  300  are coupled to sector bit lines  420 , with two main bit lines  304  from each memory block  300  selectively coupled to each sector bit line  420 . Sector bit lines  420  extend to each memory block  300 . As before, sector bit lines  420  are coupled in pairs to sense amplifiers  424 . The outputs  425  of the sense amplifiers  424  are selectively coupled to global bit line  426 . While four memory blocks  300  are depicted in FIG. 5, additional memory blocks  300  could be coupled to the sector bit lines  420  by extending the sector bit lines  420  to the additional memory blocks  300 . Note that there is no requirement that the sector bit lines  420  extend across the memory block  300  farthest from the sense amplifiers (memory block  300   0  in the embodiment of FIG.  5 ); a sector bit line  420  need only extend to a point of coupling to the block pass transistors used to couple the sector bit line  420  to its associated main bit lines  304 . 
     FIG. 6 is a schematic of portions of multiple memory sectors  400  sharing a global bit line  426  in accordance with one embodiment of the invention. In FIG. 6, two memory sectors  400   0  and  400   1  are selectively coupled to the global bit line  426  as described above. Note that memory sector  400   1  is inverted from memory sector  400   0  such that the sense amplifiers of memory sector  400   0  are adjacent the sense amplifiers of the other memory sector  400   1 . While such inverted positioning is not necessary, this layout permits tighter packing than if each memory sector  400  were positioned with the same orientation. Additional memory sectors  400  could be selectively coupled to the global bit line  426  in similar fashion, inverting the positioning of each memory sector  400  relative to adjacent memory sectors  400 . 
     FIG. 7 is a schematic of portions of multiple memory sectors  400  sharing a global bit line  426  in accordance with another embodiment of the invention showing inclusion of additional memory sectors  400 . The portion of a memory array depicted in FIG. 7 has four memory sectors  400 . Additional memory sectors  400  could be added in similar fashion. 
     In FIG. 7, the four memory sectors  400   0 ,  400   1 ,  400   2  and  400   3  are selectively coupled to the global bit line  426  as described above through multiplexers  728  (including selective coupling devices such as transistors  428 ). The positioning of each memory sector  400  is inverted from its adjacent memory sector  400 . While such inverted positioning is not necessary, this layout permits tighter packing than if each memory sector  400  were positioned with the same orientation. The global bit line  426  extends out from the memory sectors  400  to multiplexers and helper flip-flops (HFF)  730  for output from the memory device through the data output register. As shown in FIG. 7, a global bit line  426  may be coupled to sense amplifiers on both sides of the global bit line  426 . 
     Advantageously, for one embodiment, the spacing of global bit lines  426  is selected to be the same as the spacing of the array ground  318 . Thus, for an array ground  318  having a spacing of 16 columns, the spacing of the global bits lines  426  would be 16 columns such that each global bit line  426  is selectively coupled to 8 sense amplifiers  424  for each memory sector  400 . By choosing such spacing, each global bit line  426  can be formed in the space vertically above the array ground  318 , e.g., in the metal  2  (M 2 ) layer in the fabrication process, and extending substantially parallel to the array ground  318 . This permits formation of the global bit lines  426  without increasing the area of the semiconductor die. 
     While the foregoing embodiments depict only one global bit line  426  (or global bit line pair), it should be apparent that memory devices satisfying current storage requirements would generally have a large number of global bit lines  426 . Each global bit line  426  is selectively coupled to sense amplifiers  424  as described above. For one embodiment having 64 Meg of storage (67,108,684 bits organized as 4,194,304 words by 16 bits), a memory array is divided into four memory banks. FIG. 8 is a block diagram of a memory bank  800  for such an embodiment, each memory bank  800  having four memory sectors  400 . Each memory sector  400  in FIG. 8 has four memory blocks and 4,096 sense amplifiers selectively coupled to 512 global bit lines. Each global bit line extends to each of the four memory blocks in each of the four memory sectors. Note that a memory bank in accordance with the invention may contain one or more memory sectors of the various embodiments. Preferably, each memory sector  400  of the memory bank  800  contains the same number of memory blocks, with each memory block containing the same number of rows and columns of memory cells. 
     In the embodiment of FIG. 8, each memory sector  400 , and thus each memory block, is subdivided into four sections,  810   0 ,  810   1 ,  810   2  and  810   3 . An address applied to the memory device for a target memory cell in memory bank  800  may activate a word line or row in each memory sector  400  and across each section  810 . While a word line may be activated in each memory sector  400 , or even in each memory block, appropriate selection of block pass transistors and sense amplifiers can insure that no more than one memory cell will be coupled to any global bit line during a data read operation. 
     In a subdivided sector arrangement as shown in FIG. 8, access time to the target memory cell can be improved by locating row decoders (X decoders) on each side of the memory sector  400  and between each section  810  of the memory sector  400 . For one embodiment, each memory sector  400  of memory bank  800  includes a one-sided row decoder  812  and  814  on each side of the memory sector  400 , and two-sided row decoders  816  and  818  between adjacent sections  810  of the memory sector  400 . Each row decoder  812 ,  814 ,  816  and  818  addresses either a first group of rows, e.g., even rows, or the remaining or second group of rows, e.g., odd rows. Each section  810  of the memory sector  400  has a first row decoder on its first side for addressing the first group of rows in the memory sector  400 , and a second row decoder on its second or opposite side for addressing the remaining group of rows in the memory sector  400 . For sections  810  numbering a power of two, each one-sided row decoder  812  and  814  addresses the same group of rows. As shown in FIG. 8, one-sided row decoder  812  addresses even rows of the section  810   0 , two-sided row decoders  816  address odd rows of the sections  810   0 ,  810   1 ,  810   2  and  810   3 , two-sided row decoder  818  addresses even rows of the sections  810   1  and  810   2 , and one-sided row decoder  814  addresses even rows of the section  810   3 . 
     The global bit lines of the memory bank  800  are arranged similar to the arrangement of global bit lines  426  shown in FIG.  7 . Each global bit line of memory bank  800  is selectively coupled to eight sense amplifiers in each sector, which may include four sense amplifiers per sector on each side of the global bit line or all selectively coupled sense amplifiers on the same side of the global bit line. Thus, in the embodiment depicted in FIG. 8, each global bit line is selectively coupled to a total of 32 sense amplifiers. The global bit lines may be formed in the M 2  layer using the spacing of the array ground formed in the M 1  layer. The memory bank  800  further multiplexes the global bit lines for input to helper flip-flops to provide the necessary signal drive for data output. 
     It should be recognized that while the structure of memory bank  800  depicted in FIG. 8 exemplifies an array organization in accordance with the invention, it is not a complete depiction of all circuitry associated with a memory bank. Other circuitry may be included between and surrounding the memory sectors  400 , such as column decoders and write circuitry. Furthermore, other memory banks in accordance with the invention may contain fewer or more memory sectors, and each memory sector may be subdivided into fewer or more sections. Additionally, memory arrays may contain fewer or more memory banks. 
     The terms memory cell, memory block, memory sector, and memory bank have been used to describe increasingly higher-level views of a memory array. However, the invention includes memory array structures as described herein relative to these terms, and should not be limited to any preconceived notion of what these terms may convey. 
     CONCLUSION 
     Various embodiments of the invention have been shown to have architectures suited for high-performance memory devices, with particular reference to synchronous non-volatile memory devices. Memory devices in accordance with the various embodiments of the invention include blocks of memory cells arranged in columns with each column of memory cells coupled to a main bit line. Such memory devices further include sector bit lines having multiple main bit lines selectively coupled to each sector bit line, with each sector bit line extending to main bit lines in each memory block of a memory sector. Sector bit lines are coupled to sensing devices and the output of each sensing device is selectively coupled to a global bit line, with each global bit line selectively coupled to more than one sensing device. For embodiments having multiple sectors, the global bit lines may extend to more than one sector. The global bit lines are multiplexed and input to helper flip-flops for output to the data output registers of the memory device. Accordingly, the relationship between data inputs to global bit lines, global bit lines to sensing devices, and sensing devices to main lines is, in each case, typically a one-to-many relationship in the various embodiments of the invention. This array organization permits tight packing of individual memory cells with high-speed access capabilities. 
     Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement that is calculated to achieve the same purpose may be substituted for the specific embodiments shown. Many adaptations of the invention will be apparent to those of ordinary skill in the art. Accordingly, this application is intended to cover any adaptations or variations of the invention. It is manifestly intended that this invention be limited only by the following claims and equivalents thereof.