JPH07273299A - Semiconductor memory device and its manufacture - Google Patents

Abstract

PURPOSE:To increase the integration degree of stored data by a method wherein sidewalls are formed selectively on side faces of a word line, the active region of a memory cell is changed, the ON-current value of the memory cell is changed and a plurality of memory cells whose electric characteristic is different are formed. CONSTITUTION:Sidewalls 32 are formed selectively on both sides of sidewalls of word lines 22, and four kinds of memory cell transistors M0, M1, M2, M3 are formed. Then, the value of a current flowing in a memory cell is detected by a sense circuit at the outside, and the threshold value and the channel resistance value of active regions 24 at this time are judged. Then, on the basis of a judged result, whether a memory cell as an object is any of the M0 to the M3 is judged. Thereby, stored data in the memory cell can be made multivalued at a ternary value or higher, and the integration degree of data can be enhanced by an area which is identical to that of a binary memory cell as in conventional cases.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly integrated, low-priced read-only semiconductor device (ROM) semiconductor memory device and a method for manufacturing the same.

[0002]

2. Description of the Related Art A mask RO which is a type of non-volatile memory
In M, data is written according to the mask pattern at the manufacturing stage, and since the basic configuration of each memory cell is 1 bit 1 transistor, the occupied area per bit is smaller than other rewritable memories, and a large capacity, It has characteristics suitable for mass production. Taking advantage of this feature, in recent years, in the field of application of mask ROM mainly for OA devices and games that handle a large amount of fixed data, large capacity, high speed, and product cycle have been made for high functionality and high performance of products. Due to this, there is a strong demand for short delivery times, and development is proceeding to meet such demands.

At present, in order to increase the capacity, 8 megabits have entered into a full-scale mass production system, and 16 megabits are starting up. In addition, the development of 32 Mbit is coming to the end. Basic configuration is 1 bit 1
The memory cell of the mask ROM composed of transistors has memory cell size, operating speed, TAT (Turn Aro
In consideration of the “Und Time”, a large-capacity ROM of 2 megabits or more, which is currently commercialized, has a configuration shown in FIG.
There are two types: a NOR type flat memory cell type (first conventional example) as shown in FIG. 0 and a NAND type type (second conventional example) as shown in FIG.

[First Conventional Example] A first conventional example shown in FIGS. 40 to 42 is a NOR type flat memory cell type memory cell in which the number of contacts per bit is reduced (contactless structure). In order to significantly reduce the area and increase the degree of integration, as shown in FIGS. 40 to 42, the N ⁺ -type diffusion layer 1 to be the bit line is formed, and then the polycide gate 2 to be the word line is made orthogonal to it. It was formed. Polycide gate 2 for each memory cell
The source / drain 3 is formed at the intersection between the N ⁺ type diffusion layer 1 and the N ⁺ type diffusion layer 1, and a channel (active region) 4 is formed in a space between a pair of adjacent source / drain 3. In such a configuration, the gate length of each memory cell is defined by the space length between adjacent N ⁺ type diffusion layers 1, and the gate width is defined by the width of the polycide gate 2. In the first conventional example, the data writing operation (program injection step) is performed after the gate electrode is formed. Therefore, if the memory cell intermediate product after the gate electrode is formed is prepared, any data writing can be performed. It is possible to deal with short delivery times.

[Second Conventional Example] A second conventional example shown in FIGS. 43 to 45 is a NAND type ROM. Figure 4
Reference numeral 11 in FIGS. 3 to 45 denotes an N ⁺ type diffusion layer which becomes a bit line,
Reference numeral 12 is a polycide gate that becomes a word line, 13 is a source / drain, and 14 is a channel. In the second conventional example, a plurality of memory cells are vertically stacked to form a NAND for the N ⁺ type diffusion layer 11 (bit line), and the gate length is reduced by fine processing and process technology. Furthermore, by stacking 16 memory cells, high integration is achieved. Since the memory cells are stacked in 16 stages with respect to the N ⁺ type diffusion layer 11 (bit line), the read current of the memory cell is small, and in order to achieve high speed and low voltage, it is necessary to devise a circuit design. In the second conventional example, since the data writing process is performed before the polycide gate 12 is formed, the number of processes after the data writing process is increased.
It is difficult to deal with the short delivery time as compared with the conventional example.

[Third Conventional Example] FIG. 46 is a plan view showing the outline of a semiconductor memory device (sequential access memory) of the third conventional example. In FIG. 46, WL is a word line and B
L is a bit line, DXc is an X for decoding the word line WL
Address decoder, DYc is a Y address decoder for decoding the bit line BL, Dc is each address decoder DX
An element for selecting the word line WL or the bit line BL in c and DYc, and PL is a predecode line. Also,
FIG. 47 is a circuit diagram showing the outline of the periphery of the decoder section of the semiconductor memory device of the third conventional example. Dc01 and D in FIG. 47
c02, ... Decoder section, Pd01, ... Predecoder section, PL01, PL02, PL03 predecode lines, Cnt counter, Lα decoder section Dc0
1, Dc02, ... and predecode lines PL01, PL
02 and PL03.

In the third conventional example, as shown in FIG.
The output of the counter Cnt is supplied to the predecoder unit Pd01, ...
.. and decoder sections Dc01, Dc02 ,. That is, the signals once decoded by the predecoder units Pd01, ... Are predecode lines PL01, PL as shown in FIG.
02 and PL03 pass through the memory cell array in the X direction (word line WL) and the Y direction (bit line BL), and the X address decoder DXc and the Y address decoder D, respectively.
After being decoded again by Yc, the selection signal is finally transmitted to the word line WL and the bit line BL. In the third conventional example, the word line WL, the bit line BL, and the predecode lines PL01, PL02, PL03 are shown in FIG.
, A plurality of predecode lines PL01, PL02, P
They are connected by a multiple bus system using L03 as a bus.

[Fourth Conventional Example] FIG. 52 schematically shows a general memory cell array. Normally, when reading data, a set of blocks in the horizontal direction is selected. Figure 52
In, for example, the one-stage portion of the block (0,0), the block (1,0) ... Is selected and the data is read. FIG. 53 shows a block configuration of a memory cell array of a fourth conventional example, and FIG. 54 shows a configuration of a reference circuit (reference transistor array) for setting a reference value for similarly determining the type of memory cell. Fig. 53
M0 to m7 are memory cell transistors, n0 to n9
Is each source of the memory cell transistors m0 to m7
Nodes connected to the drain, m8 to m17 are block selection transistors, 201 is a main bit line made of aluminum or the like, 202 is a virtual GND line made of aluminum or the like, 203
Is a local bit line formed of a diffusion layer, BWL0 is a block selection word line gate-input to the block selection transistors m8 to m12, BWL1 is a block selection word line gate input to the block selection transistors m13 to m17, and SWL0 to SWLn. Is a switching word line for selecting each memory cell transistor. Also, in FIG. 54, MA is a memory cell array, SA is a differential sense amplifier, and RA is a reference transistor mini-array.

In FIG. 53, for example, when reading data of a memory cell transistor of m5, BWL0 is "H", BWL1 is "L", SWLn is "H", and other S.
Set WL to "L". At this time, the main bit line 201
Considering the current path from to the virtual GND line 202, firstly, (1) the main bit line 201, (2) memory cell transistor m10, (3) node n7, (4) memory cell transistor m5, (5) node n6. , (6) through memory cell transistor m9, (7) virtual GND line 202
Current flows into. Then, in the fourth conventional example, the reference transistor mini-array RA is arranged outside the memory cell array MA.

[0010]

[Problems to be Solved by the Invention]

[Problems of First Conventional Example and Second Conventional Example] In the memory cells of the first conventional example and the second conventional example described above, FIG.
As shown in FIG. 8, the data is “0” or “1” depending on whether or not a current flows between the source / drain of one memory cell that is the target of data reading, that is, one transistor. It is determined whether there is. That is, in the conventional memory cell, one memory cell corresponds to 1-bit data. Note that (0) in FIG. 48 shows the case of a memory cell in which no current flows when turned on, and (i) shows the case of a memory cell in which a current flows when turned on.

However, there is a limit in reducing the chip size of the ROM with such a configuration, and particularly in a 32-megabit ROM, for example, about 90% of the chip area is limited.
Since the memory cell array is occupied by the memory cell array, the chip size can be significantly reduced with the same degree of miniaturization technology. Need to change.

[Problem of Fourth Conventional Example] Also in the fourth conventional example, as in the first conventional example and the second conventional example, one memory cell for data read, that is, 1
Whether data is "0" or "1" is determined depending on whether or not a current flows between the source / drain of the transistor. In order to realize a large-capacity ROM with such a configuration, as in the first conventional example and the second conventional example, a drastic reduction in chip size cannot be expected unless the manufacturing process is miniaturized.

In view of the above-mentioned problems, the present invention has the same degree of miniaturization of cells as the above-mentioned conventional examples,
It is an object of the present invention to provide a semiconductor memory device that can reduce the chip size and improve the data integration degree, and a manufacturing method thereof.

Further, in the fourth conventional example, let us consider a case where the memory cell m5 is read, for example. At this time, for the word line, BWL0 and SWLn are set to "H", and the other word line S
The memory cell m5 is selected by setting WL0 ..., BWL1 to "L".

Here, from the main bit line 201, the virtual GND
Considering the current path to line 202, main bit line 201
→ m10 → n7 → m5 → n6 → m9 → virtual GND line 20
A current path such as 2 is generated.

However, here, when m6 is an "ON" transistor, from the main bit line → m11 → n8 → m6 →
There is a path of n7. When m4 is an “ON” transistor, a path of n6 → m4 → n5 → m8 → virtual GND is created. As described above, depending on whether the programming states of the transistors m4 and m6 on both sides of the target memory cell m5 are “ON” or “OFF”, in the fourth conventional example, from the main bit line 201 to the virtual GN.
The resistance value of the entire system up to the D line 202 is largely different, and the apparent ON current value of the memory cell fluctuates accordingly. Therefore, there is a problem that a current error occurs when the memory cell data is referenced by the reference circuit provided outside the memory cell array.

In view of the above problems, the present invention provides a semiconductor memory device capable of correcting a current error due to a resistance of a current path to a memory cell when the data of the memory cell is referred to by a reference circuit, and a manufacturing method thereof. That is also the purpose.

[Problem of Third Conventional Example] In the semiconductor memory device of the third conventional example, as shown in FIG. 47, predecode lines PL (PL01, PL02,
It is necessary to drive PL03) and have decoder units Dc01, Dc02, ... As many as the number of word lines WL and bit lines BL. Therefore, as the capacity increases, the predecode lines PL (PL01, PL02, PL03) become longer, and as the number of predecode lines PL increases, Wx and Wy in FIG. 46 increase and the area of each address decoder DXc and DYc increases. To do. In FIG. 47, the predecoder unit Pd01, ...
.. is limited to 3 and the data from the counter is limited to 2 bits. Therefore, each predecode line PL0
The number of wirings in 1, PL02 and PL03 is four, and the total number of predecode lines PL is twelve. Further, as shown in FIG. 47, the number of wirings Lα connecting the decoder units Dc01, Dc02, ... And the predecode lines PL01, PL02, PL03 is 2 ⁶ because of the multiple bus system. However, for example, when it is applied to about 16 mega (2 ²⁴ ) bits in practice, 28 predecode lines PL are required as a whole. Further, since the number of the wirings Lα is 2 ^{11 in} the X address decoder DXc and 2 ¹³ in the Y address decoder DYc, the predecode lines PL01 and P01 per line are provided.
The length of L02 and PL03 must be large. Since the predecode lines PL (PL01, PL02, PL03) become long, there is a problem that the processing speed is reduced and the current consumption is further increased. In addition, the chip price increases because the area increases.

In view of the above problems, it is another object of the present invention to provide a semiconductor memory device capable of realizing a low cost, high speed and low current consumption by reducing the layout area of the peripheral circuit of the memory cell array. .

[0020]

According to a first aspect of the present invention, there is provided a semiconductor memory device in which a plurality of memory cells having a gate, a gate insulating film, an active region, a source and a drain are arranged. , At least some of the memory cells have a threshold value of the active region set differently from that of other memory cells, and a 0th type memory cell, and a first resistance value in the active region. It is set to either the first type memory cell provided or the second type memory cell provided with the second resistance value in the active region.

According to a second aspect of the present invention, the width of the active region of the first type memory cell and the width of the active region of the second type memory cell are set to be different from each other.

According to a third aspect of the present invention, there is provided a semiconductor memory device in which a plurality of memory cells each having a gate, a gate insulating film, an active region, a source and a drain are arranged. A plurality of parallel strip-shaped bit lines for forming the source and the drain in a part of the upper layer portion of the semiconductor substrate, and the bit line for forming the gate for each memory cell above the semiconductor substrate. A plurality of parallel strip-shaped word lines formed in orthogonal directions, an active region is formed in a region between the source and the drain immediately below the word line, and the widths of the plurality of word lines are mutually different. The sidewalls are formed on at least one side of the side faces in the width direction of some of the word lines of the plurality of word lines having the same dimensions, and the sidewalls are provided. Width of the active region directly below the word line is set by the.

According to a fourth aspect of the present invention, in at least one of the memory cells, at least some of the memory cells are
A 0th type memory cell in which the threshold value of the active region is set differently from other memory cells, a 1st type memory cell in which the active region has a first resistance value, and the active region Is set to any one of the second type memory cells having the second resistance value, and the side wall in the width direction side face of the word line corresponding to the first type memory cell is omitted. The sidewalls of the memory cells of the second type are formed on at least one side of the corresponding word line in the width direction.

According to a fifth aspect of the present invention, in each of the memory cells, a 0th class memory cell in which the threshold value of the active region is set differently from other memory cells, and the active region is A first type memory cell having a first resistance value, a second type memory cell having a second resistance value in the active region, and a third resistance value in the active region. The side wall in the width direction of the word line corresponding to the memory cell of the first type is set to any one of the memory cells of the third type, and the side wall is omitted. Is formed only on one side of the side surface in the width direction of the corresponding word line, and the side walls of the memory cells of the third type are formed on both sides of the side surface in the width direction of the corresponding word line.

According to a sixth aspect of the present invention, the active region length of the first type memory cell and the active region length of the second type memory cell are set to be different from each other.

According to a seventh aspect of the present invention, there is provided a semiconductor substrate, a source and a drain formed in the upper layer of the semiconductor substrate for each memory cell, and each memory cell sandwiched between the source and the drain. An active region, a gate insulating film formed on at least the upper surface of the active region, and a plurality of parallel strip-shaped word lines for forming a gate on the upper surface of the gate insulating film immediately above the active region. The widths of the plurality of word lines are set to be equal to each other, a sidewall is formed on at least one side of a width direction side surface of a part of the word lines of the plurality of word lines, and the sidewall is formed depending on the presence or absence of the sidewall. The length of the active region sandwiched between the source and the drain is set.

According to an eighth aspect of the present invention, in at least one of the memory cells, at least some of the memory cells are
A 0th type memory cell in which the threshold value of the active region is set differently from other memory cells, a 1st type memory cell in which the active region has a first resistance value, and the active region Is set to any one of the second type memory cells having the second resistance value, and the side wall in the width direction side face of the word line corresponding to the first type memory cell is omitted. The sidewalls of the memory cells of the second type are formed on at least one side of the corresponding word line in the width direction.

According to a ninth aspect of the present invention, in each of the memory cells, a 0th type memory cell in which the threshold value of the active region is set differently from other memory cells, and the active region is A first type memory cell having a first resistance value, a second type memory cell having a second resistance value in the active region, and a third resistance value in the active region. The side wall in the width direction of the word line corresponding to the memory cell of the first type is set to any one of the memory cells of the third type, and the side wall is omitted. Is formed only on one side of the side surface in the width direction of the corresponding word line, and the side walls of the memory cells of the third type are formed on both sides of the side surface in the width direction of the corresponding word line.

The means for solving the problem according to claim 10 of the present invention is
A semiconductor memory device in which a plurality of memory cells each having a gate, a gate insulating film, an active region, a source, and a drain are arranged, wherein at least some of the memory cells have 0-th area in the active region. 0th type memory cell having the threshold value characteristic, the first type memory cell having the first threshold value characteristic in the active region, and the second threshold value in the active region. It is set to any one of the second type memory cells having the value characteristic.

The problem solving means according to claim 11 of the present invention is
A semiconductor memory device in which a plurality of memory cells each having a gate, a gate insulating film, an active region gate, a gate insulating film, an active region, a source, and a drain are arranged, each memory cell being a 0th memory cell in the active region. 0th type memory cell having the threshold value characteristic, the first type memory cell having the first threshold value characteristic in the active region, and the second threshold value in the active region It is set to any one of a second type memory cell having a characteristic and a third type memory cell having a third threshold characteristic in the active region.

The problem solving means according to claim 12 of the present invention is
A semiconductor substrate, a source and a drain formed in the upper layer of the semiconductor substrate for each memory cell, an active region sandwiched by the source and the drain for each memory cell, and formed at least on the upper surface of the active region. The memory cell includes a gate insulating film and a plurality of parallel strip-shaped word lines for forming a gate in a region directly above the active region on the upper surface of the gate insulating film, and each memory cell has a zeroth region in the active region. 0th type memory cell having threshold characteristics, 1st type memory cell having first threshold characteristics in the active region, 2nd threshold characteristic in the active region Of the second type of memory cells and the third type of memory cells of the active region having the third threshold characteristic.

The problem solving means according to claim 13 of the present invention is
What is claimed is: 1. A semiconductor memory device in which a plurality of memory cells having a gate, a gate insulating film, an active region, a source and a drain are arranged. A plurality of parallel strip-shaped bit lines for forming, and a plurality of parallel strip-shaped word lines formed on the upper side of the semiconductor substrate in a direction orthogonal to the bit lines to form the gate for each memory cell. An active region is formed in a region between the source and the drain immediately below the word line, and each memory cell has a 0th threshold characteristic in the active region. Memory cells, a first type memory cell having the first threshold characteristic in the active region, and a second type memory cell having the second threshold characteristic in the active region. Moriseru, and it is set to one of the third third class memory cells which are allowed to have a threshold characteristic in the active region.

The problem solving means according to claim 14 of the present invention is
The threshold values of the respective active regions of the memory cells of the respective types different from each other are set by adjusting the injection amount of the program injection.

The problem solving means according to claim 15 of the present invention is
Separation bands for separating active regions of different memory cells are formed in regions between the adjacent word lines, and sidewalls are formed on at least one side of a width direction side surface of the word lines. Also, isolation implantation is performed using the sidewall as a mask.

The problem solving means according to claim 16 of the present invention is
A semiconductor including a plurality of memory cells arranged vertically and horizontally, a plurality of connection lines to which the plurality of memory cells are connected and arranged in parallel in one direction, and an address decoder for selecting the plurality of connection lines In the storage device, the address decoder is connected to each shift line in the form of a column, and a flip-flop connected to each of the connection lines, and each flip-flop of the shift register is connected to the flip-flop by a single bus method. A first bus for inputting a clock signal and a second bus for connecting at least one of a set signal and a reset signal to each flip-flop of the shift register by a single bus system are provided.

The problem solving means according to claim 17 of the present invention is
A plurality of memory cells arranged vertically and horizontally, a plurality of word lines connected to the plurality of memory cells and arranged in parallel in one direction, and a plurality of word lines connected to the plurality of memory cells and orthogonal to the word lines. A bit line, a first address decoder for selecting the plurality of word lines, and a second address decoder for selecting the plurality of bit lines. Of the address decoder and the second address decoder, a shift register in which flip-flops respectively corresponding to the word lines or the bit lines are arranged in a row, and a single bus system for each flip-flop of the shift register. A first bus for inputting a clock signal, and a set signal and a reset connected to each flip-flop of the shift register by a single bus method Comprising respectively a second bus for inputting at least one of degree.

The problem solving means according to claim 18 of the present invention is
The set input terminal of only the most advanced flip-flop of the shift register is connected to the second bus line, and the reset input terminals of the other flip-flops are connected to the second bus line.

A means for solving the problems according to claim 19 of the present invention is
A high-speed clock generation circuit is provided on the first bus bar.

The problem solving means according to claim 20 of the present invention is
The shift register of the first address decoder and the shift register of the second address decoder are connected in series with each other.

The problem solving means according to claim 21 of the present invention is
A method of manufacturing a semiconductor memory device, comprising a gate, a gate insulating film, an active region, a source and a drain, and arranging at least three types of memory cells of the 0th to 2nd types according to the characteristics of the active region. A step of forming the gate insulating film on at least a part of an upper surface of the semiconductor substrate, and a plurality of parallel strips for forming the source and the drain for each memory cell on a part of an upper layer portion of the semiconductor substrate. A step of forming a bit line, and a step of selectively forming a plurality of parallel strip-shaped word lines for forming the gate for each of the memory cells on an upper surface of the gate insulating film in a direction orthogonal to the bit line. And a step of selectively forming a sidewall on at least one side of a width direction side surface of the word line of the second type memory cell among the plurality of word lines, Isolation implantation into the cell isolation region of the semiconductor substrate using the gate lines and the sidewalls as masks, and program-implantation into the semiconductor substrate of only the 0th type memory cell among the plurality of memory cells to perform the active region The threshold value of is set to a value different from that of other memory cells.

The problem solving means according to claim 22 of the present invention is
A method of manufacturing a semiconductor memory device, comprising a gate, a gate insulating film, an active region, a source and a drain, and arranging four kinds of memory cells of 0th to 3rd groups according to the difference in characteristics of the active region, A step of forming the gate insulating film on at least a part of an upper surface of the semiconductor substrate, and a plurality of parallel strip-shaped bits for forming the source and the drain for each memory cell on a part of an upper layer portion of the semiconductor substrate. A step of forming a line, and a step of selectively forming a plurality of parallel strip-shaped word lines for forming the gate for each memory cell on the upper surface of the gate insulating film in a direction orthogonal to the bit line. Of the plurality of word lines, sidewalls are selectively formed on both sides of a width direction side of the word line of the third type memory cell, and the word of the second type memory cell is formed. Selectively forming a sidewall only on one side of the side surface in the width direction, performing isolation injection into the cell isolation region of the semiconductor substrate using the word line and the sidewall as a mask, and a plurality of the memory cells Program injection into the semiconductor substrate of only the 0th type memory cell among them to set the threshold value of the active region to a value different from that of the other memory cells.

The problem solving means according to claim 23 of the present invention is
A method of manufacturing a semiconductor memory device having a gate, a gate insulating film, an active region, a source and a drain, and arranging at least three types of memory cells of the 0th to 2nd types according to the difference in threshold characteristics of the active region. And a step of forming the gate insulating film on at least a part of an upper surface of the semiconductor substrate, and a step of selectively forming the source and the drain for each memory cell on a part of an upper layer portion of the semiconductor substrate. A step of forming a plurality of parallel strip-shaped word lines for forming a gate on a region directly above the active region sandwiched between the source and the drain on the upper surface of the gate insulating film, and using the word line as a mask A step of performing isolation implantation in the cell isolation region of the semiconductor substrate,
A step of program-implanting at least a part of the memory cells into the semiconductor substrate to set threshold characteristics of each active region, wherein the step of setting the threshold characteristics is performed by the second type memory cells. Masking the memory cells of the 0th type and the memory cells of the 1st type into the respective semiconductor substrates, and masking the memory cells of the 1st type and the memory cells of the 2nd type. Program injection into the semiconductor substrate of the 0th type memory cell.

The problem solving means according to claim 24 of the present invention is
A method for manufacturing a semiconductor memory device having a gate, a gate insulating film, an active region, a source and a drain, and arranging four kinds of memory cells of 0th to 3rd types according to the difference in threshold characteristics of the active region. And a step of forming the gate insulating film on at least a part of the upper surface of the semiconductor substrate, and a step of selectively forming the source and the drain for each memory cell on a part of an upper layer portion of the semiconductor substrate,
Forming a plurality of parallel strip-shaped word lines for forming a gate in a region directly above the active region sandwiched by the source and the drain on the upper surface of the gate insulating film; and using the word line as a mask, the semiconductor The method further comprises the steps of performing isolation implantation into the cell isolation region of the substrate, and performing program implantation into at least some of the memory cells into the semiconductor substrate to set threshold characteristics of the active regions. In the step of setting the characteristic, the third type memory cells are masked and program injection is performed on the respective semiconductor substrates of only the zeroth type memory cells, the first type memory cells and the second type memory cells. And a step of masking the memory cells of the second type and the memory cells of the third type so that only the memory cells of the 0th type and the memory cells of the first type are masked. Program injection into each semiconductor substrate, and the semiconductor substrate having only the 0th type memory cells by masking the 1st type memory cells, the 2nd type memory cells and the 3rd type memory cells And a program injection step.

The problem solving means according to claim 25 of the present invention is
A method of manufacturing a semiconductor memory device, comprising a gate, a gate insulating film, an active region, a source and a drain, and arranging at least three types of memory cells of the 0th to 2nd types according to the characteristics of the active region. A step of forming the gate insulating film on at least a part of the upper surface of the semiconductor substrate, and a step of forming a plurality of parallel strip word lines for forming a gate for each memory cell on the upper surface of the gate insulating film. A step of selectively forming a sidewall on at least one side of a width direction side surface of the word line of the second type memory cell among the plurality of word lines; and the semiconductor using the word line and the sidewall as a mask. A step of forming a source and a drain for each memory cell by diffusing impurities in a part of an upper layer portion of the substrate; And program implanted into the semiconductor substrate of only the memory cell and a step of setting a threshold value different from the other memory cell value of the active region.

The means for solving the problems according to claim 26 of the present invention is as follows.
A method of manufacturing a semiconductor memory device, comprising a gate, a gate insulating film, an active region, a source and a drain, and arranging four kinds of memory cells of the 0th to 3rd types according to the characteristics of the active region. A step of forming the gate insulating film on at least a part of an upper surface of the semiconductor substrate; and a step of forming a plurality of parallel strip-shaped word lines for forming a gate for each memory cell on the upper surface of the gate insulating film. ,
Sidewalls are selectively formed on both sides of the word line of the third type memory cell in the width direction, and one side of the word line of the second type memory cell in the width direction. Selectively forming a sidewall only on the above, and a step of forming a source and a drain for each memory cell by performing impurity diffusion in a part of an upper layer portion of the semiconductor substrate using the word line and the sidewall as a mask, Program injecting into the semiconductor substrate of only the 0th type memory cell of the plurality of memory cells to set the threshold value of the active region to a value different from other memory cells.

The problem solving means according to claim 27 of the present invention is
Method for manufacturing a semiconductor memory device having a gate, a gate insulating film, an active region, a source and a drain, and arranging at least three types of memory cells of the 0th to 2nd types according to the difference in threshold characteristics of the active region A step of forming the gate insulating film on at least a part of the upper surface of the semiconductor substrate, and a plurality of parallel strip-shaped word lines for forming a gate for each memory cell on the upper surface of the gate insulating film. Forming a source and drain for each memory cell by performing impurity diffusion in a part of the upper layer portion of the semiconductor substrate using the word line as a mask, and programming the semiconductor substrate of at least a part of the memory cell. Implanting and setting the threshold characteristic of each of the active regions, and the step of setting the threshold characteristic includes And program-injecting the memory cells of the 0th type and the memory cells of the 1st type into the respective semiconductor substrates; masking the memory cells of the 1st type and the memory cells of the 2nd type; Program injection into the semiconductor substrate of the 0th class memory cell.

The means for solving the problem according to claim 28 of the present invention is
A method for manufacturing a semiconductor memory device having a gate, a gate insulating film, an active region, a source and a drain, and arranging four kinds of memory cells of 0th to 3rd types according to the difference in threshold characteristics of the active region. A step of forming the gate insulating film on at least a part of the upper surface of the semiconductor substrate, and forming a plurality of parallel strip-shaped word lines for forming a gate for each memory cell on the upper surface of the gate insulating film. And forming a source and a drain for each memory cell by performing impurity diffusion in a part of the upper layer portion of the semiconductor substrate using the word line as a mask, and program injection into the semiconductor substrate of at least a part of the memory cell. And setting a threshold characteristic of each of the active regions,
In the step of setting the threshold characteristic, each of the semiconductors of only the memory cells of the 0th class, the memory cells of the 1st class and the memory cells of the 2nd class is masked by masking the memory cells of the 3rd class. A step of performing program injection into the substrate; and further masking the second type memory cells and the third type memory cells to further add each semiconductor substrate to only the 0th type memory cells and the 1st type memory cells. Program injecting, and further program injecting into the semiconductor substrate of only the 0th type memory cells by masking the first type memory cells, the 2nd type memory cells and the 3rd type memory cells. And a process.

The problem solving means according to claim 29 of the present invention is
A reference element that is provided for each word line connected to each memory cell and sets a reference value for determining the type of each memory cell is compared with a current or voltage of the reference element and each memory cell. And a comparison circuit.

The problem solving means according to claim 30 of the present invention is
A main bit line is provided to supply current to the bit line,
A plurality of current paths for memory cells for supplying a current from the main bit line to each memory cell through the bit lines are formed, and reference bit lines connected to the plurality of reference elements provided for each word line. Is formed, a reference current path for supplying a current from the main bit line to each memory cell through the reference bit line is formed, and the number of the memory cell current path per one memory cell is one. The number is larger than the number of reference current paths per reference element.

The means for solving the problems according to claim 31 of the present invention is as follows.
A main bit line is provided to supply current to the bit line,
A current path for a memory cell that supplies a current from the main bit line to each memory cell through the bit line is formed, and a reference bit line connected to a plurality of the reference elements provided for each word line is formed. Is
A reference current path for supplying a current from the main bit line to each memory cell through the reference bit line is formed, and one memory cell current path per one memory cell and one per reference element Reference current paths are formed in the same number and in the same shape as each other, and memory cell block selection transistors for selecting one of the blocks of the memory cells are connected to the memory cell current paths. A reference block selection transistor for selecting one of the blocks of the reference element is connected to the current path, and the number of block selection transistors for each current path is set to be the same.

The problem solving means according to claim 32 of the present invention is
A plurality of memory cells are arranged, and a current path from the main bit line to the virtual GND line via the memory cell is formed for each memory cell. The current path is one of the main bit lines. A plurality of power source side local bit lines reaching the memory cells and a plurality of ground side local bit lines extending from the one memory cell to the virtual GND line are provided.

The problem solving means according to claim 33 of the present invention is
A plurality of memory cells are arranged, and a power supply side current path from the main bit line to each of the memory cells and a ground side current path from each of the memory cells to the virtual GND line are formed for each of the memory cells. The total length of the power-supply-side current path and the ground-side current path for each memory cell is set to be always constant, and the ground-side current path has a plurality of lengths for one virtual GND line. It has a ground side local bit line.

[0053]

In the semiconductor memory device according to claim 1 of the present invention,
At the time of reading, the current value flowing through the memory cell is detected by the external sense circuit, and the threshold value and the channel resistance value of the active region at this time are determined. Then, based on the determined combination of the threshold value and the channel resistance value of the active region, it is determined whether the target memory cell is the memory cell of the 0th class, the 1st class or the 2nd class. Then, the storage data of the memory cell can be multivalued into three or more values, and the data integration degree can be dramatically increased in the same area as the binary memory cell as in the conventional example.

In the semiconductor memory device according to the second aspect of the present invention, in setting the channel resistance values of the memory cells of the first type and the memory cells of the second type to be different from each other, the widths of both active regions are different from each other. Since it only needs to be performed, the channel resistance values of both memory cells can be accurately set, and malfunctions during reading can be prevented. Particularly, in the semiconductor memory device according to claim 3, claim 4 and claim 5 of the present invention, the active region width is set only by selectively forming sidewalls on the side portions of some word lines. , The channel resistance value can be set accurately by an easy method.

In the semiconductor memory device according to the sixth aspect of the present invention, in setting the channel resistance values of the memory cells of the first type and the memory cells of the second type to be different from each other, the lengths of both active regions are set to be different from each other. Since it is only necessary to make them different, it is possible to accurately set the channel resistance values of both memory cells and prevent a malfunction during reading. Particularly, in the semiconductor memory device according to claim 7, claim 8 and claim 9 of the present invention, the active region length is set only by selectively forming sidewalls on the side portions of some word lines. , The channel resistance value can be set accurately by an easy method.

Further, in the semiconductor memory device according to claims 5 and 9 of the present invention, the value of the current flowing through the memory cell is detected by the external sense circuit at the time of reading, and the threshold value of the active region and the threshold value of the active region at this time are detected. Determine the channel resistance.
Then, based on the determined combination of the threshold value of the active region and the channel resistance value, the target memory cell is set to the 0th
It is determined which one of the memory cells of the class, the first class, the second class and the third class. Then, the storage data of the memory cell can be four-valued, and the data integration degree of two bits in the conventional example can be provided in the same area as the binary memory cell as in the conventional example, and the area efficiency is almost doubled. Can be increased to

In the semiconductor memory device according to the tenth aspect of the present invention, at the time of reading, the value of the current flowing through the memory cell is detected by the external sense circuit, and the threshold value of the active region at this time is determined. Then, based on the determined threshold value of the active region, the target memory cells are classified into the 0th class, the 1st class and the 2nd class.
It is determined which one of the memory cells is a memory cell. Then, the storage data of the memory cell can be multi-valued into three or more levels,
It is possible to dramatically increase the data integration degree in the same area as the binary memory cell as in the conventional example.

In the semiconductor memory device according to the eleventh, twelfth and thirteenth aspects of the present invention, at the time of reading, the value of the current flowing through the memory cell is detected by the external sense circuit,
The threshold value of the active region at this time is determined. Then, it is determined from the threshold value of the determined active region whether the target memory cell is the memory cell of the 0th class, the 1st class, the 2nd class or the 3rd class. Then, the storage data of the memory cell can be four-valued, and the data integration degree of two bits in the conventional example can be provided in the same area as the binary memory cell as in the conventional example, and the area efficiency is almost doubled. Can be increased to

In the semiconductor memory device according to the fourteenth aspect of the present invention, the threshold value of each active region of each type of memory cell can be made different by simply adjusting the injection amount of program injection, and the threshold value of each memory cell can be made different. Multi-value data can be realized without complicating the structure.

In the semiconductor memory device according to the fifteenth aspect of the present invention, by forming the sidewall on the side surface in the width direction of the word line, the width of the separation band using the sidewall as a mask can be narrowed. That is, the active region width of each memory cell can be widened, the channel resistance value can be easily reduced, and the current efficiency can be increased to clarify the difference in the threshold characteristics of each memory cell.

In the semiconductor memory device according to the sixteenth and seventeenth aspects of the present invention, since the address decoder is provided with the shift register, data propagation between bits can be performed in the shift register. Therefore, the number of wirings can be remarkably reduced as compared with the case where data is propagated in the multiple bus system as in the third conventional example, and therefore the internal area of the address decoder can be remarkably reduced. Then, the chip size can be reduced, the access time can be shortened, and the power consumption can be reduced.

In the semiconductor memory device according to the eighteenth aspect of the present invention, the set input terminal of only the most advanced flip-flop of the shift register is connected to the second bus line, and the reset input terminals of the other flip-flops are connected to the second bus line. Since it is connected to the bus bar, only one set input is required, and after that, data can be propagated in the shift register. Therefore, the operation of the external device for data input can be simplified, and the area including the external device can be reduced.

In the semiconductor memory device according to the nineteenth aspect of the present invention, since the high speed clock generating circuit is provided on the first bus bar, the data propagation in the shift register is synchronized with the clock signal from the high speed clock generating circuit. The processing speed can be dramatically improved. Therefore, the techniques described in claims 16 and 17 can be applied to a random access memory or the like.

In the semiconductor memory device according to claim 20 of the present invention, the shift register of the first address decoder and the second register
By connecting the shift registers of the address decoders in series with each other in series, the set input to the first address decoder and the second address decoder is required only once, and the data can be propagated in the shift registers thereafter. . Therefore, the operation of the external device for data input can be simplified,
The area including external devices can be reduced.

In the semiconductor memory device manufacturing method according to the twenty-first, twenty-third, twenty-fifth and twenty-seventh aspects of the present invention, it is possible to easily manufacture a memory cell in which stored data is multivalued into three or more values. It is possible to manufacture a semiconductor memory device having a very high degree of data integration.

In the semiconductor memory device manufacturing method according to the twenty-second, twenty-fourth, twenty-sixth, and twenty-eighth aspects of the present invention, a memory cell whose storage data is quaternized can be easily manufactured, and the data integration degree can be increased. It is possible to manufacture a semiconductor memory device having an extremely high cost.

In the semiconductor memory device according to claim 29 of the present invention, first, the current value (or voltage value) of each memory cell transistor is compared with the current value (or voltage value) of the reference element by the comparison circuit, and each is compared. Determine the type of memory cell transistor. At this time, the distance of the current path from the main bit line differs depending on the arrangement of the memory cell transistors. Then, when the distance of the current path becomes large, resistance is generated in the path, and an error occurs in the electrical characteristics, making it difficult to compare with the memory cell transistor having a short current path on the same basis. Here, in the case of a multi-valued ROM in which memory cell transistors are set in various types, good accuracy is required when determining the difference in threshold value of each memory cell transistor. May be difficult. However, since the individual reference elements of the plurality of reference elements are connected to the same word line as each memory cell transistor, the reference elements whose current path distance from the main bit line is almost the same for each memory cell transistor. Therefore, by comparing the current value (or voltage value) of the memory cell transistor and the reference element corresponding to each other, it is possible to absorb the variation in the electrical characteristics based on the distance difference of the current path.

In the semiconductor memory device according to claim 30 of the present invention, the number of memory cell current paths per memory cell is set to be larger than the number of reference current paths per reference element. The voltage drop to the cell transistor can be suppressed lower than the voltage drop to the reference element. Therefore, the terminal potential of each memory cell transistor can be maintained as high as possible, leakage current from another current path from an adjacent memory cell transistor or the like can be reduced, and the accuracy of electrical characteristics can be maintained.

In the semiconductor memory device according to claim 31 of the present invention, the number of memory cell current paths per memory cell is set equal to the number of reference current paths per reference element, and each memory cell is Since the same number of block selection transistors are connected to the reference current path and each reference current path, when a current is passed through the memory cell and the reference element corresponding to the memory cell, the resistance value generated in the current path always has the same value. Therefore, the difference between the values of the currents flowing through the two elements can be reduced as much as possible. Therefore, the accuracy of determining the type of each memory cell can be improved as much as possible.

In the semiconductor memory device according to claim 32 of the present invention, a plurality of power source side local bit lines and a plurality of ground side local bit lines are formed for one memory cell, and the semiconductor memory device according to claim 33 is provided. In the device, since a plurality of ground-side local bit lines are formed for one virtual GND line, the resistance value generated in the wiring is greater than that in the case where each local bit line is formed only once. Can be reduced. Therefore, even if the number of block divisions of the memory cell is reduced, the same speedup can be realized.
The entire memory cell array area can be made smaller than the conventional example,
A large-capacity ROM can be manufactured inexpensively with a high yield.

[0071]

【Example】

[First Embodiment] <Structure> FIG. 1 is a plan view showing a semiconductor memory device according to a first embodiment of the present invention, FIG. 2 is a sectional view taken along the line AA, and FIG. 3 is a sectional view taken along the line BB. It is a figure. The semiconductor memory device according to the present embodiment is a nonvolatile N-type device in which a plurality of memory cells are arranged.
An OR type flat cell type semiconductor memory device (ROM), which realizes a four-valued memory cell by combining channel width control and threshold value control. 1 to 3
In the figure, M0 to M3 are memory cells, and 21 is p made of Si or the like.
Type semiconductor substrate, 22 is a word line made of polycide or the like for forming a gate for each memory cell, 23 is a gate insulating film made of a Si oxide film, and 24 is a part of the upper layer portion of the p type semiconductor substrate. Channel (active region), 2
Reference numerals 5 and 26 denote bit lines as n ⁺ type diffusion layers for forming a source and a drain for each memory cell, and 27
Is an isolation band (isolation region) that separates the channels 24 of different memory cells in the region between the adjacent word lines 22, 28 is an interlayer insulating film, 29 is a metal wiring, 31 is a Si oxide film or Si nitride. A surface protective film (passivation) 32 such as a film is a sidewall formed on at least one side of the side surface in the width direction of some word lines 22 of the plurality of word lines 22.

The word line 22 is the gate insulating film 23.
Is formed in a strip shape extending in a direction orthogonal to the bit lines 25 and 26 on the upper surface of the above, and a plurality of parallel lines are formed. The widths of the plurality of word lines 22 are set to be the same as each other in order to standardize the intermediate product after the formation of the word lines 22. The channel 24 is formed immediately below the word line 22 in a region sandwiched between the bit lines 25 and 26. The bit lines 25 and 26 are formed in a strip shape, and a plurality of bit lines are arranged in parallel. The isolation band 27 is formed by isolation implantation using the word line 22 and the sidewall 32 as a mask.

The memory cells M0 to M3 are of the enhancement type. Then, the memory cell M0
Of M3 to M3 (memory cell of the 0th class)
Of the channel 24 of the other memory cells M1 to M3
It is set significantly higher. In addition, the memory cell M1
The resistance value (channel resistance value) of the channel 24 of the (first type memory cell) is set relatively large (first resistance value), and the channel resistance value of the memory cell M2 (second type memory cell) is The channel resistance value of the memory cell M3 (third type memory cell) is set relatively small (third resistance value). The channel resistance value of the memory cell M0 (0th type memory cell) is set to be large like the first resistance value.
The difference in the channel resistance value is set by changing the width of each channel 24 (channel width). That is,
If the channel width is large, the channel resistance value is reduced, and conversely, if the channel width is small, the channel resistance value is increased. The channel width is set depending on whether or not the sidewall 32 is formed on the side surface of the word line 22 in the width direction. That is, the overlapping amount of the word line 22 and the separation band 27 varies depending on the presence or absence of the sidewall 32, but no current flows in the separation band 27 even if the word line 22 is selected by an external device. , The channel is widened by the width of the sidewall 32.

Specifically, the first type memory cell M1
The side wall of the word line 22 in the width direction corresponding to the above is set to have a small channel width by omitting the side wall, and thus has a large channel resistance value. The sidewall 32 of the second type memory cell M2 is formed only on one side of the corresponding word line 22 in the width direction.
Its channel width is set to medium, and therefore the channel resistance value is set to medium. The third type memory cell M3
The side walls 32 are formed on both sides of the corresponding side surfaces of the word line 22 in the width direction, so that the channel width thereof is set large and therefore the channel resistance value is set small.

In this manner, the sidewalls 32 are formed on both sides of the word line 22 (third-class memory cell M3), and the sidewalls are formed on one side (second-class memory cell M).
2), one of three types (0 type memory cell M0) which is not formed (third type memory cell M1 and 0 type memory cell M0) and which is not formed with sidewalls. By programming the channel 24 and setting the channel threshold value to be high, four types of memory cell transistors can be configured as follows.

0th type memory cell M0: channel width =
Small, threshold = high (transistor does not turn on) First type memory cell M1: channel width = small, threshold =
Enhancement Second type memory cell M2: channel width = medium, threshold =
Enhancement Third type memory cell M3: channel width = large, threshold =
enhancement.

The bit lines 25 and 26 are connected to each other as shown in FIG.
As described above, it is connected to the external sense circuit 36 via the bit line selection transistor 35. In general, a sense circuit is used to read the ROM data, but the sense circuit 36 used in this embodiment is no different from the existing one in that it detects the current value flowing through the memory cells M0 to M3. That is, the sense circuit 36 detects in which range the on-current value of the selected memory cell falls, and converts it into three-dimensional data {(A), (B), (C)}. . However, the sense circuit 36 has a threshold value capable of discriminating three kinds of current values, that is, between (0) and (i), between (i) and (ii), and (ii) in FIG.
And (iii) have threshold values set respectively. Here, FIG. 5 is an internal circuit diagram of a memory cell array composed of the memory cells M0 to M3, and FIG. 6 applies a predetermined voltage to the word line 22 (gate) of each of the memory cells M0 to M3 and a predetermined voltage. The current value (ON current value) flowing when a drain voltage is applied is shown. As shown in FIG. 6, the on-current values of the memory cells M0 to M3 are (0)
It is set differently such as ~ (iii). As shown in FIG. 4, the sense circuit 36 is connected to the determination circuit 37 via 3-bit output lines corresponding to the three-dimensional data {(A), (B), (C)}, respectively. As shown in FIG. 7, the decision circuit 37 determines the memory cells selected from the 0th to 3rd types based on the three-dimensional data {(A), (B), (C)} from the sense circuit 36. Which of the memory cells M0 to M3 is, and the three-dimensional data {(A), (B), (C)} is converted into 2-bit data (,
) Has the function to convert.

8, FIG. 9 and FIG. 10 are views showing the peripheral transistors such as the bit line selection transistor 35. FIG. 8 is a plan view, FIG. 9 is a sectional view taken along line CC of FIG. 10 is a DD sectional view of the same. The peripheral transistor is formed on the same upper surface of the p-type semiconductor substrate 21 on which the memory cells M0 to M3 are formed. In FIGS. 8 to 10, 40a is a LOCOS field oxide film, 40b is an n ⁺ -type diffusion layer forming a source and a drain, 40c is a gate insulating film, 40d is a gate, and 40e.
Is n ⁻ for making the source and the drain LDD structures.
Type diffusion region, 40f sidewalls, 40g interlayer insulating film, 40h metal wiring, 40i surface protection film (passivation) such as Si oxide film or Si nitride film, 40i
j is a contact region. MA in FIG. 4 is a memory cell array.

<How to Use> When the semiconductor memory device having the above-described structure is used, a predetermined voltage is applied to the word line 22 (gate) of the memory cells M0 to M3 to be read through the word line 22, and at the same time, the bit line selection transistor is selected. A predetermined voltage is applied to the gate 40d of the memory cell 35 to connect the bit lines 25 and 26 of the memory cells M0 to M3 to the sense circuit 36.
Electrically connect to. At this time, the memory cells M0 to M
The on-current value of No. 3 is as shown in FIG. That is,
In the case of the 0th type memory cell M0, since the threshold value of the channel 24 is high, the transistor does not turn on, and therefore the current value remains (0) = 0. In the case of the first type memory cell M1, the on-current value (i) is low because the channel resistance value is high. In the case of the second type memory cell M2, since the channel resistance value is medium, the on-current value (ii) is medium. In the case of the third type memory cell M3, the on-current value (iii) is high because the channel resistance value is low. Then, the sense circuit 36 detects in which range the on-current values of the memory cells M0 to M3 fall, and three-dimensional data {(A), (B), (C)} as shown in FIG. Convert to. Specifically, in the case of the 0th type memory cell M0, {(A), (B), (C)} = {"H", "H", "
H ″} and {″ in the case of the first type memory cell M1.
L ″, “H”, “H”}, and the second type memory cell M2
In this case, {"L", "L", "H"}, and in the case of the third type memory cell M3, {"L", "L", "L"}. The data {(A), (B), (C)} is used in the decision circuit 3
Sent to 7. The determination circuit 37 converts the three-dimensional data {(A), (B), (C)} from the sense circuit 36 into 2-bit data (,). Specifically, as shown in FIG. 7, {(A), (B), (C)} = {"H", "
H ″, “H”} (that is, the 0th type memory cell M
(When 0 is selected), (,) = (H, H),
In the case of {"L", "H", "H"} (that is, when the first type memory cell M1 is selected), (,) =
(H, L) and {"L", "L", "H"} (that is, when the second type memory cell M2 is selected)
Is (,) = (L, H) and {"L", "L", "
L ″} (that is, when the third type memory cell M3 is selected), (,) = (L, L).

As described above, each of the memory cells M0 to M3 independently has the multi-valued characteristic as the 2-bit data (,). Therefore, in the conventional example, one memory cell transistor corresponds to the 1-bit data. On the other hand, since the number of memory cell transistors in the cell array can be reduced to half that of the conventional one, the area of the cell array portion can be reduced by half. In other words, it is possible to have double the storage capacity in the same area as the conventional example. Therefore, while each miniaturization is about the same as the conventional example,
The ROM chip size can be markedly reduced to increase the data integration degree, and the cost and the capacity can be increased. Specifically, for example, in the case of a 32 megabit ROM, about 32 mega memory cells have been conventionally required, whereas in the present invention, about 16 mega memory cells are sufficient.

<Manufacturing Method> The manufacturing method of this embodiment will be described. 11, FIG. 13, FIG. 15, FIG. 17 and FIG. 19 are cross-sectional views showing the manufacturing process of the memory cell array, FIG.
4, FIG. 16, FIG. 18 and FIG. 20 are cross-sectional views showing the manufacturing process of the peripheral transistor. First, the p-type semiconductor substrate 2
A LOCOS field oxide film 40a to be an isolation region of a peripheral circuit is formed on the peripheral portion of the upper surface of 1.
Then, as shown in FIGS. 11 and 12, the gate insulating films 23 and 40c are formed by the CVD method or the like, and the p-type semiconductor substrate 21 is formed.
By masking a part of the upper surface of each of the memory cells, and implanting n ⁺ impurities into a part of the upper layer of the p-type semiconductor substrate 21 of each memory cell,
This is diffused to form bit lines 25 and 26 (source and drain). The bit lines 25 and 26 may be formed before the gate insulating film 23 is formed.

Next, the word line 22 (gate) and the gate 40d of the peripheral transistor are stacked by the CVD method using polysilicon or refractory metal polycide, and then on the upper surface of the word line 22 and the gate 40d. The Si oxide film 41 and the Si nitride film 42 are sequentially formed by a lithographic process. Then, as shown in FIGS. 13 and 14, after the Si oxide film 41 and the Si nitride film 42 are removed by etching, an n ⁻ -type impurity such as P (phosphorus) is injected and diffused into a predetermined region of the peripheral transistor to diffuse the n ⁻ -type. Diffusion area 4
0e is formed. Then, after depositing an oxide film by the CVD method, the entire surface is anisotropically etched to form the sidewalls 32 on both sides of the word lines 22 of all the memory cells M0 to M3 and the gate 40d of the peripheral transistors in the width direction.
40f is formed. The sidewalls 32 and 40f are
For example, it is formed by using a CVD oxide film or polysilicon. Since the manufacturing process up to this point is the same regardless of the type of each memory cell, it is possible to mass-produce it in advance as an intermediate product before determining the type of each memory cell. is there. The sidewall 32 is an LD of a peripheral transistor for selecting a bit line.
If it is formed at the same time as the sidewall 40f for the D configuration or the like, it is possible to prevent additional steps in the manufacturing process.

Then, based on the ROM design, about half of the second type memory cells M2, all of the third type memory cells M3 and all of the peripheral transistors are made photoresist 4.
3 (photolithography step), leaving predetermined sidewalls 32 and 40f as shown in FIGS. Then, the photoresist 43 is removed by etching.

Next, as shown in FIGS. 17 and 18, impurities such as boron (B) or BF ₂ are ion-implanted between adjacent memory cells to form isolation bands 27. Here, the word line 22 and the sidewall 32 serve as an implantation mask, and the amount of overlap between the separation band 27 and the word line 22 is shifted by the width of the sidewall 32. As a result, the channel width of each memory cell M0 to M3 can be adjusted.

Thereafter, as shown in FIG. 19, a resist 44 is formed in the entire region except the 0th type memory cell M0, and the channel 24 of the 0th type memory cell M0 is formed by program injection.
Set a sufficiently high threshold. Then, the interlayer insulating film 2
8, 40g, the metal wirings 29, 40h and the surface protection films 31, 40i are formed to form the semiconductor memory device shown in FIGS.

Thus, the sidewalls 3 are formed on all the gates of all the memory cells M0 to M3 and the peripheral transistors.
Since the process up to forming 2, 40f is mass-produced in advance as a standard intermediate product regardless of the design of the ROM, and the channel resistance value and the channel threshold value are different in the subsequent process, from the initial stage. Compared to changing the characteristics of each memory cell, the manufacturing period after designing the ROM can be significantly shortened.

[Second Embodiment] <Structure> FIG. 21 shows a semiconductor memory device according to a second embodiment of the present invention. The semiconductor memory device (RO
M) is the same as the first embodiment in that it is a non-volatile NOR type flat cell system having four-valued memory cells, but achieves the electrical characteristics of the channel only by the difference in the threshold value. This is different from the first embodiment in that Figure 2
1, M0 to M3 are memory cells, 51 is a p-type semiconductor substrate made of Si or the like, 52 is a word line made of polycide for forming a gate for each memory cell, and 53 is Si.
A gate insulating film made of an oxide film or the like, 54 is a channel (active region) formed by a part of the upper layer of the p-type semiconductor substrate, 5
Reference numeral 7 denotes an isolation band (isolation region) for separating the channels 54 of different memory cells in a region between the word lines 52 adjacent to each other, 58 an interlayer insulating film, 61 a surface of a Si oxide film or a Si nitride film, etc. Protective films (passivation) 62 are sidewalls formed on both sides of each word line 52 in the width direction.

The word line 52 is formed in the direction orthogonal to the bit line (not shown), as in the first embodiment shown in FIG. The channel 54 is formed immediately below the word line 52 in a region sandwiched by bit lines. The threshold value of each channel 54 is set by adjusting the injection amount of program injection. Specifically, the thresholds of the memory cells M0 to M3 are set as follows.

0th type memory cell M0: threshold value D0 =
Extremely high (transistor does not turn on) First type memory cell M1: Threshold value D1 = slightly high Second type memory cell M2: Threshold value D2 = Slightly low Third type memory cell M3: Threshold value D3 = Extremely low.

As described above, each type of memory cells M0 to M3
By changing the threshold value of the channel 54, the four types of memory cell transistors can be configured as described above.

The isolation band 57 is formed by isolation implantation using the word line 52 and the sidewall 62 as a mask. Thereby, the separation band 57
The width of can be narrowed. That is, each memory cell M
The channel widths of 0 to M3 can be widened, the channel resistance value can be easily reduced, and the current efficiency can be increased to clarify the difference in the threshold characteristics of the memory cells M0 to M3.

The bit lines 25 and 26 orthogonal to the word line 52 are connected to the external sense circuit 36 via the bit line selection transistor 35, as in the first embodiment shown in FIG. . The sense circuit 36 is connected to the determination circuit 37 via a 3-bit output line corresponding to the {(A), (B), (C)}, respectively. The configurations of the bit line selection transistor 35, the sense circuit 36, and the determination circuit 37 are the same as those in the first embodiment, and the description thereof will be omitted.

<How to use> When the semiconductor memory device having the above structure is used, a predetermined voltage is applied to the word line 52 (gate) of the memory cells M0 to M3 to be read through the word line 52, and at the same time, the bit line select transistor is selected. A predetermined voltage is applied to the gate 40d of the memory cell 35 to connect the bit lines 25 and 26 of the memory cells M0 to M3 to the sense circuit 36.
Electrically connect to. At this time, the memory cells M0 to M
The ON current value of No. 3 is the same as that of the first embodiment shown in FIG. That is, in the case of the 0th type memory cell M0, since the threshold value D0 of the channel 54 is extremely high, it is not turned on by the above voltage, and the ON current value (0) becomes 0. First
In the case of the memory cell M1 of the same class, the threshold current D1 is slightly high, and the on-current value (i) is low. In the case of the second type memory cell M2, the threshold value D2 is slightly low, and therefore the on-current value (ii) is slightly high. In the case of the third type memory cell M3, the threshold value D3 is extremely low, and therefore the on-current value (ii
i) becomes extremely high. Then, in the sense circuit 36,
The range of the threshold value of the channel 54 of the memory cells M0 to M3 is detected, and the three-dimensional data {(A), (B), is detected, as in the first embodiment shown in FIG.
(C)}. Specifically, in the case of the 0th type memory cell M0, {(A), (B), (C)} = {"
H "," H "," H "}, and the first type memory cell M1
In the case of, it is {"L", "H", "H"}, in the case of the second type memory cell M2, it is {"L", "L", "H"}, and in the third type memory cell M3. In case of {"L", "
L ″, “L”}. The data {(A), (B),
(C)} is transmitted to the determination circuit 37. Judgment circuit 37
Is the three-dimensional data from the sense circuit 36 {(A),
(B), (C)} is converted into 2-bit data (,). Specifically, similar to the first embodiment shown in FIG. 7,
{(A), (B), (C)} = {"H", "H", "
In the case of H ″} (that is, when the 0th type memory cell M0 is selected), (,) = (H, H), and {″
L ″, “H”, “H”} (that is, when the first type memory cell M1 is selected), (,) = (H,
L), and in the case of {"L", "L", "H"} (that is, when the second type memory cell M2 is selected), (,
) = (L, H) and {“L”, “L”, “L”} (that is, when the third type memory cell M3 is selected), (,) = (L, L) To do.

As described above, each of the memory cells M0 to M3 independently has the characteristic of 2-bit data (,). Therefore, similar to the first embodiment, each miniaturization is the same as the conventional example. Although small, the ROM chip size can be reduced to improve the data integration degree.

<Manufacturing Method> The manufacturing method of this embodiment will be described. First, according to the same procedure as in the first embodiment, p
A LOCOS field oxide film to be an isolation region of a peripheral circuit is formed around the upper surface of the type semiconductor substrate 51. Then, after the gate insulating film 53, the bit line, the word line 52 (gate) and the gate of the peripheral transistor are sequentially formed by the CVD method or the like, LDD implantation is performed on the peripheral transistor to form an n ⁻ -type diffusion region, and the entire surface is formed. Anisotropic etching is performed to form sidewalls 62 on both sides of the word lines 52 of all the memory cells M0 to M3 and the gates of the peripheral transistors in the width direction. afterwards,
Isolation implantation of B ⁺ , BF ₂ ^+, etc. is performed in the region of the separation zone 57.

Then, as shown in FIG. 22, after masking only the memory cell M3 with the photoresist 63, in order to raise the threshold value of the other memory cells M0 to M2, B ( Program injection using boron).

Next, as shown in FIG. 23, the memory cells M2, M
3 is masked by the photoresist 64, and then the semiconductor substrate 51 of each of the memory cells M0 and M1 is increased in order to increase the threshold value of the other memory cells M0 and M1.
Program injection is performed using B (boron) or the like.

Finally, as shown in FIG. 24, program injection is performed only in the memory cell M0 to form four types of memory cell transistors having different threshold values. After that, metal wiring is formed by a general MOS process. Then, the interlayer insulating film 58, the metal wiring and the surface protection film 61.
To form the semiconductor memory device shown in FIG.

[Third Embodiment] FIG. 25 is a plan view showing a semiconductor memory device according to a third embodiment of the present invention, and FIG.
28 is a sectional view taken along line EE of FIG.
FIG. 3 is an internal circuit diagram of a memory cell array. In this example,
Similar to the first embodiment in that the four-valued memory cell is realized by combining the channel length control and the threshold control,
It differs from the first embodiment in that it has a NAND type structure. 25 to 27, M0 to M3 are memory cells, 7
1 is a p-type semiconductor substrate made of Si or the like, 72 is a word line made of polycide or the like for forming a gate for each memory cell, 73 is a gate insulating film made of a Si oxide film, 7
Reference numeral 4 is a channel (active region) formed by a part of the upper layer portion of the p-type semiconductor substrate, 75 and 76 are sources and drains formed for each memory cell as n ⁺ -type diffusion layers, and 7
Reference numeral 7 denotes a region between the word lines 72 adjacent to each other, which is a separation band (LO) for separating the channels 74 of different memory cells.
COS oxide film), 78 is an interlayer insulating film, 81 is a surface protective film (passivation) such as a Si oxide film or Si nitride film, and 82 is at least the side surface in the width direction of some word lines 72 among a plurality of word lines 72. It is a sidewall formed on one side. The widths of all the word lines 72 are set to the same size.

In the semiconductor memory device of this embodiment,
The source and drain 75 and 76 are the word line 7
2 and the sidewall 82 are formed as a mask. Therefore, the length of the channel 74 sandwiched between the source and drain 75 and 76 (channel length) is set depending on the presence or absence of the sidewall 82.

Here, the channel 74 of the 0th type memory cell M0 is of the enhancement type. The other memory cells M1 to M3 are of depletion type. Further, the channel resistance value of the first type memory cell M1 is set relatively large (first resistance value), and the channel resistance value of the second type memory cell M2 is medium (second resistance value). Further, the channel resistance value of the third type memory cell M3 is set relatively small (third resistance value). The channel resistance value of the 0th type memory cell M0 is set to be large like the first resistance value. The difference in the channel resistance value is set by changing the respective channel lengths. That is, if the channel length is large, the channel resistance value is increased, and conversely, if the channel length is small, the channel resistance value is decreased. The channel length is set depending on whether the sidewall 82 is formed on the side surface of the word line 72 in the width direction. That is, the amount of overlap between the word line 72 and the sources and drains 75 and 76 differs depending on the presence or absence of the sidewall 82, and therefore the channel 74 becomes longer by the width of the sidewall 82.

Specifically, the first type memory cell M1
By forming the sidewalls 82 on both sides of the word line 72 in the width direction, the channel length thereof is set large, and thus the channel resistance value is set large. The side wall 82 of the memory cell M2 of the second type is formed only on one side of the side surface in the width direction of the corresponding word line 72, so that the channel length thereof is set to an intermediate value and therefore the channel resistance value is set to an intermediate value. Is set. The side wall 82 of the memory cell M3 of the third type has a corresponding word line 72.
By omitting it on the side surface in the width direction, the channel length is set small and therefore the channel resistance value is set small.
Similar to the first type memory cell M1, side walls 82 are formed on both sides of the word line 72 corresponding to the 0th type memory cell M0 in the width direction, so that the channel length is set to be large. The channel resistance value is set to a large value.

In this way, the sidewalls 82 are formed on both sides of the word line 72 (first type memory cell M1 and 0th type memory cell M0), and one side wall (second type memory cell). Program injection into the channel 74 of one (0th type memory cell M0) of which three types are formed: a cell M2) and a non-formed type (third type memory cell M3). Then, by setting the channel threshold value higher, four kinds of memory cell transistors can be configured as follows.

0th type memory cell M0: channel length =
Length, threshold = enhancement First type memory cell M1: channel length = length, threshold =
Depletion Second type memory cell M2: channel length = medium, threshold =
Depletion Third type memory cell M3: channel length = short, threshold =
Depression.

Also in this embodiment, one memory cell transistor can store two bits of data (four values).

At the time of manufacturing this embodiment, similarly to the first embodiment, first, the sidewalls 82 are formed on the side surfaces of the word lines 72 of all the memory cells M0 to M3, and then the necessary portions are masked with photoresist or the like. Then, both sides of the third type memory cell M3 and one side wall of the second type memory cell M2 may be selectively removed by etching. According to this embodiment, the same effect as that of the first embodiment can be obtained.

[Fourth Embodiment] FIG. 29 is a sectional view showing a semiconductor memory device according to the fourth embodiment of the present invention. This embodiment is similar to the second embodiment in that the electrical characteristics of the channel are achieved only by the difference in threshold value, but NA
It differs from the second embodiment in that it is an ND type system. 29, M0 to M3 are memory cells, 91 is a p-type semiconductor substrate made of Si or the like, 92 is a word line made of polycide or the like for forming a gate for each memory cell, and 93 is a gate made of Si oxide film or the like. An insulating film 94 is a channel (active region) formed by a part of the upper layer of the p-type semiconductor substrate,
Reference numeral 96 is a source and drain formed as an n ⁺ type diffusion layer for each memory cell, 98 is an interlayer insulating film, and 99 is a surface protective film (passivation) such as a Si oxide film or a Si nitride film.

The channel 94 is formed immediately below the word line 92 in a region sandwiched by the source and drain 95 and 96. The threshold value of each channel 94 is set by adjusting the injection amount of program injection. Specifically, the thresholds of the memory cells M0 to M3 are set as follows.

0th type memory cell M0: threshold value D0 =
Enhancement First type memory cell M1: Threshold value D1 = high depletion Second type memory cell M2: Threshold value D2 = medium depletion Third type memory cell M3: Threshold value D3 = low depletion.

Also in this embodiment, as in the third embodiment, one memory cell transistor can store two bits of data (four values).

[Fifth Embodiment] <Structure> The fifth embodiment of the present invention includes the first embodiment and the third embodiment.
In the case of further miniaturizing the cell than in the above embodiment, if the four-valued memory cell array is configured as described above,
For example, as shown in FIG. 15, in the step of forming the sidewall 32 of the second type memory cell M2 only on one side of the width direction side surface of the word line 22, photoresist is accurately formed up to the middle portion of the second type memory cell M2. It can be difficult to form. In view of such difficulty, the semiconductor memory device of this embodiment is configured by a ternary memory cell array. The semiconductor memory device (ROM) of this embodiment is of the NOR type flat cell type, and specifically, the memory cell array has memory cells M1 and M2 whose thresholds of the channel 24 are different as shown in FIG. 0th type memory cell M0 that is set differently from the above, a first type memory cell M1 in which no sidewall is formed (that is, a channel resistance value is high), and a sidewall 32 is formed in both sides.
It is composed of three types of memory cells of the memory cell M2 of the same class. Since this embodiment employs the NOR type flat cell system, no sidewall is formed in the 0th type memory cell M0. As a result, it becomes unnecessary to accurately form the photoresist up to the middle portion of the memory cell (M2 in FIG. 15) as in the first embodiment shown in FIG. Other configurations are similar to those of the first embodiment, and members having the same function are designated by the same reference numerals.

<Usage Method> Next, a specific method of reading stored data will be described. FIG. 31 shows an example of output data (on-current value) in the case of storing three values in one memory cell, and FIG. 32 shows a block diagram of a read circuit (sense circuit etc.) of the memory cell array. In this embodiment, as shown in FIG. 32, two memory cells Ma and Mb are selected, and the ON current values of the memory cells Ma and Mb are set to the sense circuits 36a and 36b.
Then, the 3-bit data is read by the judgment circuit 37. Specifically, as shown in FIG. 31, the on-current values of the memory cells Ma and Mb are (0) (i) (i) in FIG.
i) different from each other. Then, as shown in FIG. 33, when the type of the memory cell Ma is the 0th type (M0), the output signals {(A), (B)} of the sense circuit 36a are {"H", ".
H ″}, and when the type of memory cell Ma is the first type (M1), the output signals {(A), (B)} are {″.
L ″, “H”}, and when the type of memory cell Ma is the second type (M2), the output signals {(A), (B)} are {“L”, “L”}. When the type of the memory cell Mb is the 0th type (M0), the output signals {(C), (D)} of the sense circuit 36b are {"H", "H"},
When the type of memory cell Mb is the first type (M1), the output signals {(C), (D)} are {"L", "H"}, and the type of the memory cell Mb is the second type (M2). ), The output signal {(C), (D)} becomes {"L", "L"}.

The sense circuit 36 thus obtained
a, 36b output signals {(A), (B), (C),
Based on (D)}, the decision circuit 37 converts the data into 3-bit data (,,). Specifically, as shown in FIG. 33, {(A), (B), (C), (D)} = {"
L "," L "," L "," L "} (that is, M
When a and Mb are both M2), (,,) =
(L, L, L), {(A), (B), (C),
(D)} = {"L", "L", "L", "H"} (that is, when Ma is M2 and Mb is M1) (,
,) = (L, L, H), and {(A), (B),
(C), (D)} = {"L", "L", "H", "
In the case of H ″} (that is, when Ma is M2 and Mb is M0), (,,) = (L, H, L),
{(A), (B), (C), (D)} = {"L", "
H "," L "," L "} (that is, Ma is M1,
When Mb is M2), (,,) = (L, H, H)
And {(A), (B), (C), (D)} = {”
L "," H "," L "," H "} (that is, Ma
Is M1, and Mb is M1) is (,,) = (H,
L, L) and {(A), (B), (C), (D)} =
In the case of {"L", "H", "H", "H"} (that is, when Ma is M1 and Mb is M0), (,,) =
(H, L, H), {(A), (B), (C),
(D)} = {"H", "H", "L", "L"} (that is, when Ma is M0 and Mb is M2) (,
,) = (H, H, L), and {(A), (B),
(C), (D)} = {"H", "H", "L", "
In the case of H ″} (that is, when Ma is M0 and Mb is M1), (,,) = (H, H, H) is set.
In the case of this embodiment, the output of the pair of sense circuits 36a and 36b is 3 ² = 9 types, whereas the output of the determination circuit 37 is 2 ³ = 8 types.
The remaining one of the outputs of 6a and 36b, that is, {(A),
(B), (C), (D)} = {"H", "H", "
In the case of H ″, “H”} (that is, when both Ma and Mb are M0), they are used as error detection data.

As described above, since the storage data can be multi-valued for the transistors forming the memory cell, one memory cell transistor corresponds to 1-bit data in the conventional example, while In the case of a value memory cell, one memory cell transistor can store 1.5-bit data, and a memory device of the same capacity (RO
In the case of configuring M), the number of memory cell transistors can be reduced to 2/3 of the conventional one. Therefore, the chip size can be remarkably reduced, and the cost and the capacity can be increased.

<Manufacturing Method> The manufacturing method of this embodiment will be described. First, as in the first embodiment shown in FIGS. 11 and 13, after stacking the bit lines 25 and 26 and the word line 22 on the p-type semiconductor substrate 21, all the memory cells M0 to M3 are stacked.
Sidewalls 3 on both sides of the word line 22 in the width direction.
Form 2. Then, based on the ROM design, the second
The entire area of the memory cell M2 of the second class is covered with a photoresist (photolithography step), and the surface oxide film is removed by etching, so that the side wall 3 of the memory cell M2 of the second class is formed.
Leave 2. At this time, unlike the first embodiment, it is not necessary to coat the photoresist with high precision up to the middle of the memory cell, so that an extremely fine memory cell array can be dealt with. After that, the word line 22 and the sidewall 3
Impurities such as boron (B) or BF ₂ are ion-implanted using 2 as an implantation mask to form a separation zone 27. Here, the amount of overlap between the separation band 27 and the word line 22 is shifted by the width of the sidewall 32. Thereby, the channel width of each memory cell M0-M2 can be adjusted. After that, the threshold value of the 0th type memory cell M0 is set sufficiently high by program injection, the interlayer insulating film 28, the metal wiring 29, and the surface protection film 31 are formed to form the semiconductor memory device shown in FIG. To be done.

[Sixth Embodiment] In order to use a semiconductor memory device (mask ROM) as a substitute for a CD-ROM device, for example, it is necessary to have a large capacity, a low speed, and a low price. Since it is a substitute for a CD-ROM device, the mask ROM can sufficiently perform sequential access. The semiconductor memory device according to the sixth embodiment of the present invention is
As shown in FIG. 34, which is a sequential access memory (ROM), a memory cell array 101 in which a plurality of memory cells are arranged vertically and horizontally and a plurality of the memory cells in the memory cell array 101 are connected and arranged in one direction. It is provided with a plurality of connection lines 102 provided and an address decoder 104 for selecting the plurality of connection lines 102.

The memory cell array 101 has the first
It may be a ROM array as in the embodiments 5 to 5, or a rewritable memory array such as EPROM, EEPROM, flash memory, or RAM.

The connection line 102 includes both a word line for gate input of each memory cell in the memory cell array 101 and a bit line for drain signal input,
The word lines and bit lines are formed so as to be orthogonal to each other. The connection line 102 is provided with a buffer 105 for amplifying each bit output and transmitting a selection signal to each memory cell.

The address decoder 104 includes a first address decoder (X address decoder) for selecting the plurality of word lines and a second address decoder (Y address decoder) for selecting the plurality of bit lines. ) Is included. Then, the address decoder 1
Reference numeral 04 denotes a shift register 106 in which flip-flops FF0 to FF3 corresponding to the connection lines 102 are arranged in a row, and a single clock input terminal (CK) of each of the flip-flops FF0 to FF3 of the shift register 106. First bus bar 1 for clock signal input connected in bus system
07 (clock line) and a second bus line 108 (set / reset line) for inputting a reset signal, which is connected to the reset input terminals (bar R) of the flip-flops FF0 to FF3 of the shift register 106 in a single bus system. ) And. In addition, the data output terminals (Q) of the flip-flops FF0 to FF2 of the shift registers 106 and the data input terminals (D) of the flip-flops FF1 to FF3 adjacent to the flip-flops FF0 to FF2 are connected to each other, and further, the leading edge ( 1
The data input terminal (D) of the (th) flip-flop FF0 and the data output terminal (Q) of the last flip-flop FF3 are connected to each other. The data input terminals (D) of the flip-flops FF0 to FF3 are connected to the buffer 105 on the connection line 102. With this configuration, the required area of each address decoder 104 is smaller than that of the shift register 106 and the first bus bar 107.
Moreover, the area is sufficient for forming the second bus bar 108, and the area can be sufficiently reduced as compared with the third conventional example in which the wiring is spread around in the multiple bus system, and the cost can be reduced.

In the above structure, first, when the power is turned on and the chip is reset, the reset signal is applied from the second bus line 108 to reset the shift register 106.
At this time, the memory cell is in a non-selected state.

At the start of the sequential access, "1" data is input to the data input terminal (D) of the most advanced (first) flip-flop FF0. Then, the data array of (FF0, FF1, FF2, FF3) becomes (1, 0, 0, 0), and only the buffer 105 of the connection line 102 corresponding to the most advanced (first) flip-flop FF0 is turned on, Other flip-flops FF1 to F
The buffer 105 of the connection line 102 corresponding to F3 is turned off. Next, when a clock signal is transmitted from the first bus line 107 to operate the shift register 106, "1" data propagates through the shift register 106 and transits to the subsequent flip-flop. At this time, "0" data is input to the data input terminal (D) of the most advanced (first) flip-flop FF0. Then, (FF0, FF1, FF
2, FF3) = (0,1,0,0), and only the buffer 105 of the connection line 102 corresponding to the second flip-flop FF1 is turned on. After that, every time a clock signal is transmitted from the first bus line 107, “0” data is input to the data input terminal (D) of the frontmost (first) flip-flop FF0. Then, (FF0, FF1, FF
2, FF3) is (0,0,1,0), (0,0,0,
1), and flip-flops FF2 and FF3, respectively
Only the buffer 105 of the connection line 102 corresponding to is sequentially turned on. After that, when the sector address changes,
Again, "1" data is input to the data input terminal (D) of the frontmost (first) flip-flop FF0. By repeating the above operation in this manner, the outputs of the flip-flops FF0 to FF3 of the shift register 106 are amplified by the buffer and the selection signals are sequentially transmitted to the connection line 102 (word line or bit line). The memory cells can be accessed sequentially.

In this embodiment, while the area of each address decoder is reduced as described above, the same operation as in the third conventional example can be realized, and the power consumption is reduced by reducing the number of wirings by reducing the area. Reduction can be achieved and at the same time processing speed can be improved. Specifically, for example, 2 megawords × 16 bits [= 32 megabits] or 4 megawords × 16 bits [=
64 megabits], the maximum access time for each part is 2.0 μs for sector access tas, 500 μs for maximum intra sector access tas, and cycle time tcy.
The minimum c is 500 μs (2 MHz), the maximum chip select access tce is 2.0 μs, and the maximum OE access toe is 100 μs. The access time of the CD-ROM (excluding seek time, during continuous reading) is 6.7 μs.
/Byte=13.4 μs / word, 4 × speed CD-
Since it is 3.35 μs / word in ROM, CD-RO
Compared with M, access time can be shortened significantly.

[Seventh Embodiment] Although the semiconductor memory device of the seventh embodiment of the present invention is a sequential access mask ROM similar to that of the sixth embodiment, the address decoder 10 is used.
The configuration of the shift register 106 in FIG. 4 is different from that of the sixth embodiment.

That is, the semiconductor memory device of this embodiment is
As shown in FIG. 35, a large capacity sequential access mask R
Of the flip-flops FF0 to FFn of the shift register 106, the second bus line 108 is connected to the set input terminal (bar S) of the frontmost (first) flip-flop FF0. The other flip-flops FF1 to FFn have a second reset input terminal (bar R).
Bus line 108 is connected. And the second bus 108
Is connected to a pulse device (bar SATD) that outputs a LOW pulse as a SATD signal at the time of a sector address (X address) address transition. The other structure is similar to that of the sixth embodiment. FIG. 36 is a diagram showing the relationship between the clock signal (ck), the sector address (sa), the selected bit line (ps) and the pulse (SATD) from the pulse device (bar SATD). In this way, a pulse device (SA
TD), a LOW pulse is generated, and this signal sets the frontmost (first) flip-flop FF0 of the shift register 106, and the other flip-flops FF1.
~ Reset FFn. The subsequent operation is similar to that of the sixth embodiment. Also according to this embodiment, the same effect as that of the sixth embodiment can be obtained.

[Eighth Embodiment] Sequential access mask ROM of the sixth and seventh embodiments.
In the (semiconductor memory device), the adjacent flip-flops in the shift register 106 are transferred after waiting for the input of the clock signal. When applying the technique, if the number of flip-flops in the shift register 106 is large in the case of a large-capacity memory, a clock time (usually about 1 μs) is required until all bits are selected.
× It takes time for the number of flip-flops, and there is a limit to improvement of processing speed. Therefore, in the eighth embodiment of the present invention, as shown in FIG. 37, the high speed clock generating circuit 111 is connected to the shift register 106 to accelerate the transition speed of the data in the shift register 106. In FIG. 37, ct is a counter and AND is an AND circuit.

At the time of reading, as shown in FIG. 37, the sector address is input to the counter in synchronization with the bar SATD signal. The high-speed clock generation circuit 111 generates a clock that is sufficient for the shift register 106 to operate and that is as fast as possible regardless of an external clock. Specifically, the high-speed clock time of the high-speed clock generation circuit 111 is set to about 10 ns. With this clock, the counter is decremented and the shift register 106 is operated until it becomes zero. This speed is
Since the access time of this mask ROM is sufficiently short, it does not affect the access time. By using the present invention, the area of the X address decoder can be reduced and the cost can be reduced. The internal structure of the address decoder is similar to that of the sixth or seventh embodiment, and further, the internal operation of the address decoder, for example, the specific data propagation operation of the shift register 106 of the present embodiment is the sixth. The procedure is the same as that described in the above embodiment and the seventh embodiment.

In this embodiment, the clock time is about 1/1000 of the 1 μs of the sixth and seventh embodiments.
Since the data transfer speed of the shift register 106 can be dramatically increased, the random access mask ROM does not decrease the processing speed,
Moreover, the same effects as those of the sixth and seventh embodiments can be obtained. In particular, when the X address decoder that specifies the sector address adopts the random access method, if the X address decoder and the Y address decoder have the same configuration, the processing speed of both becomes unbalanced. If the counter and the high-speed clock signal are used for the X address decoder as in the present embodiment with the same configuration as the sixth embodiment or the seventh embodiment, X
The address decoder can be processed at the same processing speed as the Y address decoder. When applied to a sequential access mask ROM, the overall processing speed can be significantly increased.

[Ninth Embodiment] The semiconductor memory device of the ninth embodiment of the present invention is a high speed FIFO (First In First Out) of the sequential access memory.
t Memory). FIG. 38 is a plan view showing the semiconductor memory device of this embodiment. Similar to the sixth embodiment, the semiconductor memory device of this embodiment has a memory cell array 101 in which a plurality of memory cells are arranged vertically and horizontally.
And a plurality of connection lines 102 connected to the plurality of memory cells in the memory cell array 101 and arranged in parallel in one direction.
And an address decoder 104 for selecting the plurality of connection lines 102, and the respective configurations of the memory cell array 101, the connection lines 102, and the address decoder 104 are the same as those in the sixth embodiment. In the FIFO of
The READ address decoders 113, 114 and W are provided to both the X address decoder (first address decoder) and the Y address decoder (second address decoder).
The RITE address decoders 115 and 116 are required respectively, and each has the same configuration as that of the sixth embodiment. However, READ Y address decoder 1
The data output terminal (Q) of the last flip-flop FFn of the shift register 106 of No. 14 and the data input terminal (D) of the most front end (first) flip-flop FF0 of the shift register 106 of the READ X address decoder 113. ) And are connected in series with each other. Similarly,
The data output terminal (Q) of the last flip-flop FFn of the shift register 106 of the WRITE Y-address decoder 116 and the frontmost (first) flip-flop FF0 of the shift register 106 of the WRITE X-address decoder 115. The data input terminals (D) are connected in series with each other. In each Y address decoder 114, 116, the data output terminal (Q) of the last (final) flip-flop FFn of the shift register 106 and the data input terminal (D) of the last (first) flip-flop FF0 are They are connected in series with each other. Then, when the pulses are sequentially transited in the shift register 106 of each of the Y address decoders 114 and 116,
The last flip-flop FF of the shift register 106
The output from n is input to the most advanced flip-flop FF0 and, at the same time, the corresponding X address decoder 113, 1
Input to the shift register 106 of 15 at the same time as the clock. The output of the flip-flop FFn at the last end of the shift register 106 of each X address decoder 113, 115 is input to the frontmost flip-flop FF0 of the same shift register 106. These operations are the same for both the READ side and the WRITE side. As a result, all the memory cells can be sequentially accessed by the respective pulses of READ and WRITE. The FIFO requires a full flag and an empty flag, which are generated by comparing conventional counters (pointers for READ and WRITE). By using the present invention, the connection line (word line and bit line) 102 can be selected at high speed, and a high-speed FIFO can be realized. Further low current consumption,
Lower prices can be realized at the same time.

[Tenth Embodiment] For example, a memory cell of a multi-valued ROM as in the first to fifth embodiments has a structure similar to that of the fourth conventional example shown in FIG. Consider when to apply. First, (1) main bit line 201
From (2) memory cell transistor m10, (3) node n7, (4) memory cell transistor m5, (5)
The current path in which the current flows into the virtual GND line 202 (7) through the node n6 and (6) memory cell transistor m9 can be realized only when the memory cell transistors m4 and m6 are “OFF” transistors. When the memory cell transistors m4 and m6 are "ON" transistors, first, as a current path, from the main bit line 201 of the above (1), the memory cell transistor m11, the node n8, the memory cell transistor m6,
From the path flowing in the order of the node n7 and the node n6 in the above (5), the memory cell transistor m4, the node n5,
A path that flows in the order of the memory cell transistor m8 and the virtual GND line 202 is added.

Comparing the memory cell transistor m1 and the memory cell transistor m5 in FIG. 53, the local bit line 203 from the main bit line 201 to the memory cell transistor m1 is short for the memory cell transistor m1. While the resistance value is as low as several hundreds Ω, in the memory cell transistor m5, the local bit line 203 from the main bit line 201 is longest and the resistance value is as high as several KΩ to several tens KΩ).

In this way, the current path is complicated,
When the length of the local bit line 203 varies greatly depending on the location of the memory cell transistor selected,
For example, when the memory cell is multi-valued as in the first to fifth embodiments, the apparent ON current value may significantly change and a malfunction may occur.

Further, as shown in FIG. 54, when the reference circuit for setting the reference value for judging the type of the memory cell is constituted by the mini-array independent of the memory cell array, the memory cell is turned on due to the process variation. The current value and the ON current value of the reference transistor fluctuate, which causes a malfunction, and the resistance value of the local bit line 203 greatly differs depending on the position of the memory cell transistor selected as described above.
A large difference appears in the N current value. And it is impossible to absorb this difference with the configuration of FIG.

Therefore, in the tenth embodiment of the present invention, as shown in FIG. 49, a plurality of reference transistors mr are provided.
By incorporating 2, mr3 (reference element) in the memory cell transistor array 210 and setting the memory cell transistors m12 and m13 under substantially the same conditions, the above-mentioned variations in the ON current value are absorbed. 49, m16 and m17 are block selection transistors, m12 and
m13 is a memory cell transistor, 211 is a main bit line, and SA is a differential sense amplifier as a comparison circuit for comparing the current values of the memory cell transistors m12 and m13 and the reference transistors mr2 and mr3.

FIG. 50 shows a block circuit of the memory cell array 210 of this embodiment. The memory cell array 210 of the semiconductor memory device of this embodiment is a ternary ROM including the same three types of memory cell transistors as those of the fifth embodiment shown in FIG. In FIG. 50, BWL is a block selection word line, m10, m11, m16 and m17 are block selection transistors, n0, n1 and n2 are nodes connected to the source / drain of the memory cell transistors m12 and m13, and SWL0 to SWLn are A memory cell transistor selection switching word line for gate input to the memory cell transistors m12 and m13, m14a,
m14b and m15 are memory cell transistors m12 and m
The transistors n3 and n4 for deciding which one of the transistors 13 to select are the transistors m15.
Connected to the source / drain of RWL, LW
L is a word line input to the transistors m14a, m14b and m15, 211 is a main bit line made of aluminum or the like, 212 is a virtual GND made of aluminum or the like.
Lines 213 are local bit lines. In addition, a transistor whose gate is drawn with a thick line in FIG. 50 is an OFF transistor, and a transistor whose gate is drawn with a thin line is an ON transistor.

The memory cell transistors m12 and m1
3 includes three types of memory cell transistors as described above. Therefore, each memory cell transistor m12, m
A reference circuit as shown in FIG. 51 is required as a reference transistor that serves as a reference value for determining which type 13 is. As shown in FIG. 51, the reference transistors mr2 and mr3 are arranged for each memory cell transistor selection switching word line SWL0 to SWLn in the memory cell array 210. Here, FIG. 51 is a diagram showing a region arranged laterally of the memory cell array MA shown in FIG.
Wirings BWL and RW shown in FIGS. 51 and 50
L, LWL, SWL0 to SWLn are the same.
In FIG. 51, a transistor whose gate is drawn with a thick line is an OFF transistor, and a transistor whose gate is drawn with a thin line is an ON transistor. Further, in the reference circuit shown in FIG. 51, the transistors mr located next to the reference transistors mr2 and mr3, respectively.
51 and 4 are ON transistors in FIG. 51, they are generally OFF transistors to prevent a current from flowing in from the side. Further, m10a, m11a, m16a and m17a in FIG. 51 are reference selection transistors for selecting the reference transistors mr2 and mr3, 211a is a main bit line made of aluminum or the like, 212a is a virtual GND line made of aluminum or the like, 213a. Is a local bit line. Then, all the transistors gate-connected to RWL and LWL are OFF transistors. As a result, as will be described later, the reference current path for each of the reference transistors mr2 and mr3 is single, and the individual memory cell transistors m12 and m13 are provided.
The number is set smaller than the number (two) of current paths for memory cells per memory cell. At the time of reference, the main bit line 211
a serves as a reference input of the differential sense amplifier SA. Since the present embodiment is a three-value ROM, two reference values are required to distinguish these three values.
Generally, in the case of a multi-valued ROM, reference transistors are required for each type of memory cell transistors except "OFF" transistors. For example, four values require three reference transistors, and five values require four reference transistors.
Therefore, instead of using the reference transistors of these numbers for data storage, they may be replaced with respective types of reference transistors. Specifically, in the case of a ROM that can take three values (0, 1, OFF), both mr2 and mr3 in FIG. 51 are "0" transistors, and both mr2 and mr3 are "1".
It suffices to configure two types of reference circuits of transistors. Similarly, in the case of four values, three types of reference circuits are configured.

The operation of the semiconductor memory device having the above configuration will be described by taking the case of selecting m13 in FIG. 50 as an example. In the operation of this embodiment, the value of the memory cell transistor m13 is read by the differential sense amplifier SA shown in FIG. 49, and then the reference transistor connected to the same word line SWL0 to SWLn as the memory cell transistor m13. Read the values of mr2 and mr3.
The values of the reference transistors mr2 and mr3 may be read first and the value of the memory cell transistor m13 may be read later. In any case, BWL of the memory cell transistor m13 is "H", RWL is "L", LWL is "H", SWL0 is "H", and other SW.
Set L to "L". Consider the current path from the main bit line 211 to the virtual GND line 212 at this time. First,
As the path from the main bit line 211 to the memory cell transistor m13, the path from the memory cell transistor m11 to the node n2 and the block selection transistor m1
7 → node n2, and the path from the memory cell transistor m13 to the virtual GND line 212 is node n1 → memory cell transistor m15a → node n3 → block selection transistor m10 and node n1 → memory cell transistor m15b. -> Node n4-> block selection transistor m16.

Here, considering the influence of the local bit line 213, in the conventional example of FIG. 53, assuming that the resistance value of each local bit line 213 is R, the maximum value of the resistance of the current path is approximately 2R. On the other hand, in the case of this embodiment shown in FIG. 50, since two paths are formed, the maximum value of the resistance becomes approximately 1 / 2R, and the local bit line 21
The influence of the resistance value of 3 is 1/4 of that of the conventional example. As a result, the range of the apparent ON current value depending on the position of the selected memory cell transistor can be reduced.

In addition, considering the case where m13 is "ON" and "OFF" in FIG. 50, the resistance value of the local bit line 213 is ignored and the lower half (SW
(Ln or less) is ignored, and the virtual GN is
Considering the resistance value up to D as the resistance of one transistor is R, in the case of FIG. 50, if m12 is “OFF”, 4
If R and m12 are "ON", it becomes 7 / 2R, and the ratio is
It becomes 1: 1.14. Similarly, in the case of FIG. 53, m10, m
When both 12 are “OFF”, they are 3R and when they are “ON”, they are 7 / 3R, and the ratio is 1: 1.29, and the influence of the state of surrounding memory cell transistors is also improved by the present invention.

Further, in the present invention, as shown in FIG. 51, the reference transistors mr2 and mr3 are arranged inside the memory cell array 210. Therefore, for example, when the m12 transistor is selected in FIG. 50, the same SWL0 as the reference is selected. The transistors whose gates are (mr2 and mr3 in FIG. 51) are selected. As a current path, when reading m13 in FIG. 50 for one path of mr3 → mr2 in the reference circuit, m13
→ m15a / m13 → m15b / m13 → m12 / Since there are many (three) paths, it is guaranteed that the reference currents mr2 and mr3 always have a lower ON current value. The same applies to the case. In this way, a difference in distance between the memory cell transistor connected to a certain word line and the memory cell transistor connected to another word line (local bit line 213) occurs in the current path to the transistor, Even if there is a difference in the resistance value of the current path, that is, a difference in the current value flowing through the memory cells, the reference transistor is connected to the same word line as each memory cell, so the bit line for reading data is connected. If the read transistor is the same as the reference transistor by using the same sense circuit portion and the circuit to which the reference bit line is connected, the reference O
It can be guaranteed that the N current value is low. Further, since the number of memory cell current paths per memory cell is set to be larger than the number of reference current paths per reference element, the voltage drop to each memory cell transistor is reduced to the reference transistor voltage. It can be kept lower than the descent. Therefore, the terminal potential of each memory cell transistor can be maintained as high as possible, leakage current from another current path from an adjacent memory cell transistor or the like can be reduced, and the accuracy of electrical characteristics can be maintained. From these things, the memory cell transistors m12 and m1
The threshold value of 3 is the reference transistor mr2, m
It is possible to prevent an error from occurring with respect to the reference value of r3. Therefore, it becomes possible to commercialize a multi-valued ROM having accurate electrical characteristics. As a result, when the same fine process is used, the conventional ROM is compared and 3
In the case of a value ROM, the chip area can be reduced by about 25% to 30%, and in the case of four values, it can be reduced by about 40%.

Now, this embodiment will be compared with the fourth conventional example. In the fourth conventional example shown in FIG. 53, when the data of the memory cell m5 is read, the path from the main bit line 201 to the virtual GND line 202 is m10 → n7 → m5 when the m6 and m4 transistors are OFF. → n6 →
It is one route of m9. Therefore, assuming that the resistance value of the local bit line 203 from the block selection transistor m10 to the memory cell transistor m5 is R, the maximum value is 2R.
Resistance value is added. Since this resistance value hinders high-speed operation of the memory, the memory cell array is generally divided into blocks as shown in FIG. In the case of the fourth conventional example,
For high speed operation, it is necessary to increase the number of block divisions in the vertical direction. However, then, the transistors m8 to m12 and m13 to m17 for block selection are selected.
Of the memory cell array area becomes large, and the chip size also becomes large.

On the other hand, in the present embodiment shown in FIG. 50, when the data of the memory cell transistor m13 is read, the path from the main bit lines 211 to m13 is
There are two routes, m11 → n2 and m17 → n2, and m
The path from 13 to the virtual GND line 212 is n1 → m15a → n3 → even when the m12 transistor is OFF.
There are two routes of m10 and n1 → m15b → n4 → m16. In this case, if the resistance of the local bit line 213 is R as in the above case, only a resistance value of R / 2 is added at the maximum, and the number of block divisions is 1/4 compared with the conventional example.
Even so, it is possible to achieve the same speedup. In the case of the present embodiment, the ratio of the transistors other than the memory cells in one block is about three times larger than that in the fourth conventional example, but the ratio in the entire memory cell array area is the fourth.
It can be made smaller than the conventional example. Therefore, the chip size can be reduced, and a large-capacity ROM can be manufactured at a high yield at a low cost.

[Eleventh Embodiment] <Structure> A memory cell array according to an eleventh embodiment of the present invention is shown in FIGS. 2 in FIGS. 55 and 56
Reference numeral 20 is a first block selection word line, 221 is a second block selection word line, SWL0 to SWLn are section selection word lines, 226 is a first memory cell main bit line, and 227 is a second memory cell main bit line. A bit line, 228 is a third memory cell bit line, 230 is a first memory cell virtual GND line, and 231 is a second memory cell virtual G line.
ND line, 232 is a virtual GND line for the third memory cell, 2
29 is a local bit line for memory cells, m20 is a memory cell, m21 and m22 are block selection transistors to which the first block selection word line 221 is gate-inputted, and Toff1 is an off transistor. Also, FIG.
7 and 58 show a reference circuit of this embodiment, in which mr20 is a reference transistor,
Similar to m21 and m22 in FIG. 55, m31 and m32 are block selection transistors to which the first block selection word line 221 is gate-inputted, 236 is a first reference main bit line, and 237 is a second reference A main bit line, 238 is a third reference bit line, 239 is a reference local bit line, 240
Is a first reference virtual GND line, 241 is a second reference virtual GND line, 242 is a third reference virtual GND line, and Toff2 is an off transistor.

55 to 58, a memory cell current path for supplying a current from the memory cell main bit line 227 to the memory cell m20 through the local bit line 229 is formed, and the reference main bit is formed. A memory cell current path for supplying a current from the line 237 to the reference transistor mr20 through the local bit line 239 is formed. Then, the memory cell current path connected to the one memory cell m20 and the one reference transistor mr2.
The reference current paths connected to 0 are all single paths and have the same shape.
The same number of block select transistors are connected to each memory cell current path and each reference current path. In this embodiment, a single current path is provided for each memory cell m20 and each reference transistor mr20, but the shape and number of each current path are set to be equal to each other, and the block selection transistor for each current path is set. m21, m22, m31, m3
If the numbers of 2 are set equal to each other, each memory cell m
20 and each reference transistor mr20 may be provided with a plurality of current paths.

<How to use> In the above structure, considering the data reading of the memory cell m20 of FIG. 55, the second memory cell main bit line 227 is connected to the sense circuit,
The virtual GND line 232 for the second memory cell is connected to GND. Further, one block selection word line 221 is "H", and the nth section word line SWLn is "H".
And the other word lines 220, SWL0 ... Are set to "L". Here, the current path from the second memory cell main bit line 227 to the second memory cell virtual GND line 232 is the main bit line 227 → m21 → n10 → m20 → n11.
→ m22 → Limited to a single path of the virtual GND line 232 for the second memory cell.

Considering reference data reading from the reference transistor mr20 shown in FIG. 57,
The second reference main bit line 237 is connected to the sense circuit, and the second reference virtual GND line 242 is connected to G
Connect to ND. In addition, one block selection word line 2
21 is "H", the n-th section word line SWLn is "H", and the other word lines 220, SWL0 ... Are "L".
And Here, the second reference main bit line 23
The current path from 7 to the second reference virtual GND line 242 is the main bit line 237 → m31 → n20 → mr2.
0 → n21 → m32 → second reference virtual GND
Limited to a single path of line 242.

As described above, the current path to the memory cell m20 and the current path to the reference transistor mr20 are formed in the same number and the same shape, and the number of block selection transistors that pass is the same. Therefore, the resistance values generated in the memory cell current path and the reference current path are almost completely equal.
Therefore, the accuracy in comparing these current values can be dramatically improved.

As described above, as an example, the second memory cell main bit line 227 and the second reference main bit line 237 are connected to the sense circuit, and the second memory cell virtual GND line 232 and When the second reference virtual GND line 242 is connected to GND, the other main bit lines 226, 228, 236, 238 may be precharged. In this case, for example, the block selection word line 221 and the nth section word line SWL
When n is set to “H”, all the transistors gate-input from the block selection word line 221 and the nth section word line SWLn are turned on, and the current due to precharge may flow into n10 and n20 via the transistor. However, even in these leakage current paths, the leakage current path reaching the memory cell m20 and the leakage current path reaching the reference transistor mr20 are formed in the same number and in the same shape.
In addition, the number of block selection transistors that have passed is the same, so that the resistance values generated in the memory cell current path and the reference current path are substantially equal. Therefore, even when considering the total of the current from the sense circuit and the current due to the precharge, the accuracy of the reference can be dramatically improved.

Now, this embodiment will be compared with the fourth conventional example. First, in the memory cell array configuration of the fourth conventional example shown in FIG. 53, the main bit line and the virtual GND line are actually selected, the main bit line is used as a sense circuit, and the virtual GND line is set to G.
When connecting to ND, for example, the main bit line 201 is connected to the sense circuit and the virtual GND line 202 is connected to GND. Here, in order to prevent the inflow of current from the left direction in the drawing, which is not shown, to the virtual GND line 202, in general, the virtual GND on the left side of the virtual GND line 202 is generally used.
A line (not shown) is connected to GND and the local bit line connected to it is connected to GND. That is, the adjacent virtual GND lines and the local bit lines connected to the virtual GND lines via the block selection transistor are connected to the GND.
It is common to connect to D to read data. Therefore, the main bit line / virtual G of the fourth conventional example
The ND line selection circuit 250 is generally configured as shown in FIG. 59, DL0 is a data line connected to one sense circuit in the selection circuit 250, DL1 is a data line connected to another sense circuit in the selection circuit 250, and B0 to B6 are main bit line selections. Transistor gate electrodes, G0 to G7, are gate electrodes of the virtual GND line selection transistor, respectively. Each gate electrode B0 in FIG.
.., B6, G0 to G7 input signal settings (H or L) are shown in FIG. Note that S0 to S in FIGS.
Reference numeral 7 indicates the block number of the operation target.

On the other hand, in the case of the memory cell array structure of this embodiment shown in FIG. 55, one virtual GND line is
Since the two local bit lines are connected through the block selection transistor, as in the fourth conventional example,
It is not necessary to select two virtual GND lines. Therefore, the main bit line / virtual GND line selection circuit 250 in the present embodiment has a configuration as shown in FIG. The setting of the input signals of the gate electrodes B0 to B6 of the main bit line selection transistors and the gate electrodes G0 to G7 of the virtual GND line selection transistors shown in FIG. 61 is as shown in FIG. Note that S0 to S7 in FIGS. 61 and 62 indicate block numbers of operation targets.

As can be seen by comparing FIGS. 60 and 62, in the fourth conventional example, two virtual GND lines and main bit lines on both sides thereof are selected and sandwiched between the two virtual GND lines. While it was necessary to deselect the main bit line, the other main bit lines, and the virtual GND line, in this embodiment, 1
The virtual GND line of the book and the main bit lines on both sides of the virtual GND line may be selected, and the other main bit lines and the virtual GND line may be deselected. The decoding method of this main bit line / virtual GND line is shown in FIG. Since it is simpler than the fourth conventional example, the number of elements in the decoding circuit can be reduced. Therefore, it becomes possible to reduce the chip size, and the large-capacity ROM
Can be manufactured at high cost and at low cost.

Further, in order to operate the memory at high speed, the main bit lines of the memory cell array are generally set in advance to a voltage level close to the sense level of the sense circuit. Here, in the case of the fourth conventional example, as described above, G
Since the virtual GND line connected to ND has a configuration in which one main bit line is sandwiched, current may flow from the main bit line to the virtual GND line via the block selection transistor and the memory cell transistor. Occur. Therefore, the memory cell transistor for reading is turned on.
In the case of a transistor, two main bit lines connected to the sense circuit and three main bit lines of the main bit lines sandwiched between the virtual GND lines are connected to the virtual GND line via the block selection transistor. Current flows into the two virtual GND lines via the two local bit lines.

On the other hand, in the case of the present embodiment, since the current path from the main bit line not connected to the sense circuit as in the fourth conventional example does not occur, the memory cell transistor for reading is the ON transistor. In the case of, the current flows from the two main bit lines connected to the sense circuit to one virtual GND line through the two local bit lines connected to the virtual GND line through the block selection transistor. become. As described above, in the present embodiment, since the current inflow path from the main bit line to the virtual GND line is smaller than that in the fourth conventional example, the virtual GND line is
The time required to reach the potential of ND is shortened as compared with the conventional one, and high-speed operation becomes possible.

Here, the number of virtual GND lines connected to the GND is conventionally two, but in the present embodiment, it is one, but the virtual GND line is usually made of a resistor such as aluminum. Since the material is made of a material having a sufficiently low value, the operation time is not affected if the number of local bit lines connected to the virtual GND is the same.

[Modification] (1) In the fifth embodiment, the three-valued memory cell array is formed by the NOR type flat cell system.
It may be a NAND type. In addition,
In the reference numerals in FIG. 39, those who have the same functions as those in the third embodiment are designated by the same reference numerals.

(2) In the ninth embodiment, the internal structure of each address decoder is the same as that of the sixth embodiment, but it may be the same as that of the seventh embodiment.
The configuration may be similar to that of the above embodiment.

[0156]

According to the first aspect of the present invention, at the time of reading, the current value flowing through the memory cell is detected by the external sense circuit, and the threshold value and the channel resistance value of the active region at this time are determined. Then, based on the determined combination of the threshold value and the channel resistance value of the active region, it is determined whether the target memory cell is the memory cell of the 0th class, the 1st class or the 2nd class. Then, the data stored in the memory cell can be multivalued into three or more values, and the data integration degree can be dramatically increased in the same area as the binary memory cell as in the conventional example.

According to claim 2 of the present invention, in setting both channel resistance values of the first type memory cell and the second type memory cell to be different from each other, it is only necessary to make the widths of both active regions different from each other. The channel resistance values of both memory cells can be set accurately, and malfunctions during reading can be prevented. In particular, claim 3, claim 4 and claim 5 of the present invention
In the semiconductor memory device according to the present invention, since the active region width is set only by selectively forming the sidewalls on the side portions of some word lines, it is possible to accurately set the channel resistance value by an easy method. There is.

According to the sixth aspect of the present invention, in setting the channel resistance values of the memory cells of the first type and the memory cells of the second type to be different from each other, it is only necessary to make the lengths of the two active regions different from each other. Therefore, the channel resistance values of both memory cells can be set accurately, and malfunctions during reading can be prevented. Particularly, in the semiconductor memory device according to claim 7, claim 8 and claim 9 of the present invention, the active region length is set only by selectively forming sidewalls on the side portions of some word lines. There is an effect that the channel resistance value can be accurately set by an easy method.

According to claims 5 and 9 of the present invention, the current value flowing through the memory cell is detected by the external sense circuit at the time of reading, and the threshold value and the channel resistance value of the active region at this time are determined. To do. Then, based on the determined combination of the threshold value and the channel resistance value of the active region, it is determined whether the target memory cell is the memory cell of the 0th class, the 1st class, the 2nd class or the 3rd class. .
Then, the storage data of the memory cell can be four-valued, and the data integration degree of two bits in the conventional example can be provided in the same area as the binary memory cell as in the conventional example.
There is an effect that the area efficiency can be almost doubled.

According to the tenth aspect of the present invention, at the time of reading, the value of the current flowing through the memory cell is detected by the external sense circuit, and the threshold value of the active region at this time is determined. Then, it is determined from the threshold value of the determined active region whether the target memory cell is the memory cell of the 0th class, the 1st class or the 2nd class. Then, the data stored in the memory cell can be multivalued into three or more values, and the data integration degree can be dramatically increased in the same area as the binary memory cell as in the conventional example.

According to the eleventh, twelfth and thirteenth aspects of the present invention, at the time of reading, the value of the current flowing through the memory cell is detected by the external sense circuit, and the threshold value of the active region at this time is determined. Then, based on the determined threshold value of the active region, the target memory cells are the 0th class, the 1st class,
It is determined whether the memory cell is the second type or the third type. Then, the storage data of the memory cell can be quaternaryized, and the data integration degree of two bits in the conventional example can be provided in the same area as the binary memory cell as in the conventional example, and the area efficiency is almost doubled. There is an effect that can be raised to.

According to the fourteenth aspect of the present invention, the threshold value of each active region of each type of memory cell can be made different by merely adjusting the injection amount of program injection, and the structure of each memory cell is not complicated. However, there is an effect that multi-value data can be realized.

According to the fifteenth aspect of the present invention, by forming the sidewall on the side surface in the width direction of the word line, the width of the separation band using the sidewall as a mask can be narrowed. That is, the active region width of each memory cell can be widened, the channel resistance value can be easily reduced, and the current efficiency can be increased, whereby the difference in the threshold characteristic of each memory cell can be clarified.

According to the sixteenth and seventeenth aspects of the present invention, since the address decoder is provided with the shift register, data propagation between bits can be performed in the shift register. Therefore, the number of wirings can be remarkably reduced as compared with the case where data is propagated in the multiple bus system as in the third conventional example, and therefore the internal area of the address decoder can be remarkably reduced. Then, there is an effect that the chip size can be reduced, the access time can be shortened, and the power consumption can be reduced.

According to the eighteenth aspect of the present invention, the set input terminal of only the most advanced flip-flop of the shift register is connected to the second bus line, and the reset input terminals of the other flip-flops are connected to the second bus line. Therefore, only one set input is required, and after that, data can be propagated in the shift register. Therefore, the operation of the external device for data input can be simplified, and the area including the external device can be reduced.

According to claim 19 of the present invention, since the high speed clock generating circuit is provided on the first bus bar, the data propagation in the shift register can be synchronized with the clock signal from the high speed clock generating circuit, and the processing speed can be increased. Can be dramatically improved. Therefore, claim 16 and claim 1
There is an effect that the technique described in 7 can be applied to a random access memory or the like.

According to the twentieth aspect of the present invention, by connecting the shift register of the first address decoder and the shift register of the second address decoder in series with each other, the first address decoder and the second address decoder are connected. The set input of is required once, and then the data can be propagated in the shift register. Therefore, the operation of the external device for data input can be simplified, and the area including the external device can be reduced.

The present invention claims 21, 23, and 2.
According to the fifth aspect and the twenty-seventh aspect, there is an effect that it is possible to easily manufacture a memory cell in which stored data is multivalued into three or more values, and to manufacture a semiconductor memory device having an extremely high degree of data integration.

Claims 22, 24 and 2 of the present invention
According to the sixth aspect and the twenty-eighth aspect, there is an effect that a memory cell in which stored data is quaternized can be easily manufactured, and a semiconductor memory device having an extremely high degree of data integration can be manufactured.

According to claim 29 of the present invention, since each reference element among the plurality of reference elements is connected to the same word line as each memory cell transistor,
For each memory cell transistor, there exists a reference element having the same current path distance from the main bit line. By comparing the current value (or voltage value) of the corresponding memory cell transistor and reference element, Therefore, there is an effect that variations in electrical characteristics based on the distance difference between current paths can be absorbed.

According to claim 30 of the present invention, since the number of memory cell current paths per memory cell is larger than the number of reference current paths per reference element, each memory cell transistor is reached. The voltage drop can be suppressed to be lower than the voltage drop reaching the reference element. Therefore, there is an effect that the terminal potential of each memory cell transistor can be maintained as high as possible, a leakage current from another current path from an adjacent memory cell transistor or the like can be reduced, and the accuracy of electrical characteristics can be maintained. .

According to claim 31 of the present invention, the number of memory cell current paths per memory cell is set equal to the number of reference current paths per reference element, and each memory cell current path and Since the same number of block selection transistors are connected to each reference current path, when a current is passed through the memory cell and the reference element corresponding to the memory cell, the resistance value generated in the current path is always the same value. It is possible to reduce the difference between the current values flowing through the two elements as much as possible. Therefore,
There is an effect that the type determination accuracy of each memory cell can be improved as much as possible.

According to claim 32 of the present invention, a plurality of power source side local bit lines and a plurality of ground side local bit lines are formed for one memory cell, and according to claim 33, one virtual GND is provided. Since a plurality of ground side local bit lines are formed for each line, the resistance value generated in the wiring can be reduced as compared with the case where each local bit line is formed only once. Therefore, even if the number of block divisions of the memory cell is reduced, the same speedup can be realized, so that the entire memory cell array area can be made smaller than the conventional example, and a large capacity ROM can be manufactured at a high yield at a low cost. There is.

[Brief description of drawings]

FIG. 1 is a plan view showing a semiconductor memory device according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a sectional view taken along line BB of FIG.

FIG. 4 is a block diagram showing a peripheral circuit in the semiconductor memory device according to the first embodiment of the present invention.

FIG. 5 is a circuit diagram showing a memory cell array of the semiconductor memory device according to the first exemplary embodiment of the present invention.

FIG. 6 is a diagram showing a relationship between each memory cell and an on-current value of the semiconductor memory device according to the first embodiment of the present invention.

FIG. 7 is a diagram showing output data in each unit of the semiconductor memory device according to the first embodiment of the present invention.

FIG. 8 is a plan view showing a peripheral circuit of the semiconductor memory device according to the first exemplary embodiment of the present invention.

9 is a cross-sectional view taken along line CC of FIG.

10 is a cross-sectional view taken along line DD of FIG.

FIG. 11 is a diagram showing a manufacturing process of the semiconductor memory device according to the first embodiment of the present invention.

FIG. 12 is a diagram showing a manufacturing process of the semiconductor memory device according to the first embodiment of the present invention.

FIG. 13 is a diagram showing a manufacturing process of the semiconductor memory device according to the first embodiment of the present invention.

FIG. 14 is a diagram showing a manufacturing process of the semiconductor memory device according to the first embodiment of the present invention.

FIG. 15 is a diagram showing a manufacturing process of the semiconductor memory device according to the first embodiment of the present invention.

FIG. 16 is a diagram showing a manufacturing process of the semiconductor memory device according to the first embodiment of the present invention.

FIG. 17 is a diagram showing a manufacturing process of the semiconductor memory device according to the first embodiment of the present invention.

FIG. 18 is a diagram showing a manufacturing process of the semiconductor memory device according to the first embodiment of the present invention.

FIG. 19 is a diagram showing a manufacturing process of the semiconductor memory device according to the first embodiment of the present invention.

FIG. 20 is a diagram showing a manufacturing process of the semiconductor memory device according to the first embodiment of the present invention.

FIG. 21 is a sectional view showing a semiconductor memory device according to a second embodiment of the present invention.

FIG. 22 is a diagram showing a manufacturing process of the semiconductor memory device according to the second embodiment of the present invention.

FIG. 23 is a diagram showing a manufacturing process of the semiconductor memory device according to the second embodiment of the present invention.

FIG. 24 is a diagram showing a manufacturing process of the semiconductor memory device according to the second embodiment of the present invention.

FIG. 25 is a plan view showing a semiconductor memory device according to a third embodiment of the present invention.

26 is a sectional view taken along line EE of FIG. 25.

27 is a cross-sectional view taken along the line FF of FIG.

FIG. 28 is a circuit diagram showing a memory cell of a semiconductor memory device of Example 3 of the present invention.

FIG. 29 is a sectional view showing a semiconductor memory device according to a fourth embodiment of the present invention.

FIG. 30 is a diagram showing a semiconductor memory device according to a fifth embodiment of the present invention.

FIG. 31 is a diagram showing the relationship between each memory cell and the on-current value of the semiconductor memory device according to the fifth embodiment of the present invention.

FIG. 32 is a block diagram showing a peripheral circuit in a semiconductor memory device according to a fifth example of the present invention.

FIG. 33 is a diagram showing output data in each unit of the semiconductor memory device according to the fifth embodiment of the present invention.

FIG. 34 is a circuit diagram showing an outline of a semiconductor memory device according to a sixth embodiment of the present invention.

FIG. 35 is a circuit diagram showing the outline of a semiconductor memory device according to a seventh embodiment of the present invention.

FIG. 36 is a diagram showing waveforms at various parts of the semiconductor memory device according to the seventh embodiment of the present invention.

FIG. 37 is a block diagram showing an outline of part of a semiconductor memory device according to an eighth embodiment of the present invention.

FIG. 38 is a plan view showing the outline of a semiconductor memory device according to a ninth embodiment of the present invention.

FIG. 39 is a sectional view showing a semiconductor memory device of a modified example of the invention.

FIG. 40 is a plan view showing a semiconductor memory device of a first conventional example.

41 is a sectional view taken along line GG of FIG. 40.

42 is a cross-sectional view taken along the line HH of FIG. 40.

FIG. 43 is a plan view showing a semiconductor memory device of a second conventional example.

44 is a cross-sectional view taken along the line I-I of FIG. 40.

45 is a sectional view taken along line JJ of FIG. 40.

FIG. 46 is a plan view showing the outline of a semiconductor memory device of a third conventional example.

FIG. 47 is a circuit diagram showing an outline of a peripheral circuit portion of a semiconductor memory device of a third conventional example.

FIG. 48 is a diagram showing output data in each unit of the semiconductor memory devices of the first conventional example and the second conventional example.

FIG. 49 is a circuit block diagram schematically showing a semiconductor memory device according to a tenth embodiment of the present invention.

FIG. 50 is a circuit diagram showing a memory cell array of a semiconductor memory device according to a tenth embodiment of the present invention.

FIG. 51 is a circuit diagram showing the vicinity of a reference element of a semiconductor memory device according to a tenth embodiment of the present invention.

FIG. 52 is a schematic diagram showing a memory cell array of a fourth conventional example.

FIG. 53 is a circuit diagram showing a memory cell array of a fourth conventional example.

FIG. 54 is a circuit block diagram showing an outline of a semiconductor memory device of a fourth conventional example.

FIG. 55 is a circuit diagram showing a memory cell array of a semiconductor memory device according to an eleventh embodiment of the present invention.

FIG. 56 is a layout configuration diagram showing a wiring shape of a memory cell array of a semiconductor memory device according to an eleventh embodiment of the present invention.

FIG. 57 is a circuit diagram showing the vicinity of a reference element of a semiconductor memory device according to an eleventh embodiment of the present invention.

FIG. 58 is a layout configuration diagram showing a wiring shape near a reference element of a semiconductor memory device according to an eleventh embodiment of the present invention.

FIG. 59 is a diagram showing a main bit line and virtual GND line selection circuit of a semiconductor memory device of a fourth conventional example.

FIG. 60 is a diagram showing setting of an input signal of each gate electrode in a main bit line and virtual GND line selection circuit of a semiconductor memory device of a fourth conventional example.

FIG. 61 is a diagram showing a main bit line and virtual GND line selection circuit of a semiconductor memory device according to an eleventh embodiment of the present invention.

FIG. 62 is a diagram showing setting of an input signal of each gate electrode in a main bit line and virtual GND line selection circuit of a semiconductor memory device according to an eleventh embodiment of the present invention.

[Explanation of symbols]

 M0 type 0 memory cell M1 type 1 memory cell M2 type 2 memory cell M3 type 3 memory cell 21 semiconductor substrate 22 word line 23 gate insulating film 24 active region 25, 26 bit line 27 isolation band 32 Side wall 51 Semiconductor substrate 52 Word line 53 Gate insulating film 54 Active region 57 Separation band 62 Side wall 71 Semiconductor substrate 72 Word line 73 Gate insulating film 74 Active region 75,76 Source and drain 82 Side wall 91 Semiconductor substrate 92 Word line 93 Gate insulating film 94 Active region 95, 96 Source and drain 101 Memory cell array 102 Connection line 104 Address decoder FF0 to FFn Flip-flop 106 Shift register 107 First busbar 108 Second busbar 111 High-speed clock generation times 113 to 116 Address decoder 210 Memory cell array 211 Main bit line 212 Virtual GND line 213 Local bit line 220,221 Block selection word line SWL0 to SWLn Section selection word line m20 Memory cell m21, m22 Block selection transistor 226 to 228 Main for memory cell Bit line 229 Local bit line 230 to 232 Virtual GND line for memory cell mr20 Reference transistor m31, m32 Block selection transistor 236 to 238 Main bit line for reference 239 Local bit line 240 to 242 Virtual GND line for reference

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location G11C 17/00 305

Claims (33)

[Claims] 1. A semiconductor memory device in which a plurality of memory cells each having a gate, a gate insulating film, an active region, a source and a drain are arranged, wherein at least a part of the memory cells comprises:
A 0th type memory cell in which the threshold value of the active region is set differently from other memory cells, a 1st type memory cell in which the active region has a first resistance value, and the active region A semiconductor memory device to be set in any one of the second type memory cells having a second resistance value. 2. The semiconductor memory device according to claim 1, wherein the active region widths of the first type memory cells and the active region widths of the second type memory cells are set to be different from each other. 3. A semiconductor memory device in which a plurality of memory cells having a gate, a gate insulating film, an active region, a source and a drain are arranged, wherein the semiconductor substrate and a part of an upper layer portion of the semiconductor substrate are provided with the semiconductor substrate. A plurality of parallel strip-shaped bit lines for forming the source and the drain, and a plurality of parallel bit lines formed in a direction orthogonal to the bit lines for forming the gate for each memory cell above the semiconductor substrate. A strip-shaped word line, an active region is formed in a region between the source and the drain immediately below the word line, and active regions of different memory cells are separated from each other in a region between the adjacent word lines. And a width of each of the plurality of word lines is set to be the same as each other, and some of the plurality of word lines have a small width side surface in the width direction. A sidewall is formed on one side, and the isolation band is formed by isolation implantation using the word line and the sidewall as a mask, and the width of the active region sandwiched between the pair of isolation bands depending on the presence or absence of the sidewall. The semiconductor memory device in which is set. 4. A memory cell of the 0th class in which at least a part of the memory cells has a threshold value set in the active region different from that of other memory cells, and a first memory cell in the active region. A memory cell of the first class having a resistance value and a memory cell of the second class having a second resistance value in the active region; The side wall in the width direction side surface of the word line corresponding to the cell is omitted, and the side wall of the second type memory cell is formed on at least one side of the width direction side surface of the corresponding word line. 3. The semiconductor memory device according to item 3. 5. The memory cell is a type 0 memory cell in which the threshold value of the active region is set differently from other memory cells, and the active region has a first resistance value. Of the memory cell of the first class, the memory cell of the second class having the second resistance value in the active region, and the memory cell of the third class having the third resistance value in the active region The side wall in the width direction of the word line corresponding to the first type memory cell is omitted, and the side wall of the second type memory cell corresponds to the corresponding word line. 4. The semiconductor memory device according to claim 3, wherein the side wall of the memory cell of the third type is formed on only one side of the side surface in the width direction, and the side walls of the corresponding third word line are formed on both sides of the side surface in the width direction of the corresponding word line. 6. The semiconductor memory device according to claim 1, wherein the active region lengths of the first type memory cells and the active region lengths of the second type memory cells are set to be different from each other. 7. A semiconductor substrate, a source and a drain formed for each memory cell in an upper layer portion of the semiconductor substrate, an active region sandwiched between the source and the drain for each memory cell, and at least the active region. A gate insulating film formed on an upper surface; and a plurality of parallel strip-shaped word lines for forming a gate in a region directly above the active region on the upper surface of the gate insulating film. The sidewalls are formed on at least one side of the side surfaces in the width direction of some of the word lines of the plurality of word lines having the same dimensions, and the active region sandwiched between the source and the drain depending on the presence or absence of the sidewall. Storage device in which the length of the memory is set. 8. A memory cell of the 0th class in which at least a part of the memory cells is set so that a threshold value of the active region is different from that of other memory cells, and a memory cell of the first type in the active region is formed. A memory cell of the first class having a resistance value and a memory cell of the second class having a second resistance value in the active region; The side wall in the width direction side surface of the word line corresponding to the cell is omitted, and the side wall of the second type memory cell is formed on at least one side of the width direction side surface of the corresponding word line. 7. The semiconductor storage device according to 7. 9. The memory cell is a 0th type memory cell in which the threshold value of the active region is set differently from other memory cells, and the active region has a first resistance value. Of the memory cell of the first class, the memory cell of the second class having the second resistance value in the active region, and the memory cell of the third class having the third resistance value in the active region The side wall in the width direction of the word line corresponding to the first type memory cell is omitted, and the side wall of the second type memory cell corresponds to the corresponding word line. 8. The semiconductor memory device according to claim 7, wherein the side wall of the memory cell of the third type is formed only on one side of the side surface in the width direction, and the side walls of the corresponding third word line are formed on both sides of the side surface in the width direction of the corresponding word line. 10. A semiconductor memory device in which a plurality of memory cells having a gate, a gate insulating film, an active region, a source and a drain are arranged, wherein at least a part of the memory cells is
A 0th type memory cell having the 0th threshold characteristic in the active region, a 1st type memory cell having the 1st threshold characteristic in the active region, and the active region A semiconductor memory device set in any of the second type memory cells having the second threshold characteristic. 11. A semiconductor memory device in which a plurality of memory cells having a gate, a gate insulating film, an active region, a source and a drain are arranged, wherein the memory cell has a zeroth threshold value in the active region. A 0th class memory cell having a characteristic, a first class memory cell having a first threshold value characteristic in the active region, and a second threshold value characteristic having a second threshold value characteristic in the active region. A second type of memory cell and a third type of memory cell in which the active region has a third threshold value characteristic. 12. A semiconductor substrate, a source and a drain formed for each memory cell in an upper layer portion of the semiconductor substrate, an active region sandwiched between the source and the drain for each memory cell, and at least the active region. A gate insulating film formed on an upper surface of the gate insulating film; and a plurality of parallel strip-shaped word lines for forming a gate in a region directly above the active region on the upper surface of the gate insulating film. A zeroth type memory cell having a zeroth threshold characteristic, a first type memory cell having a first threshold characteristic in the active region and a second type memory cell in the active region. A semiconductor memory set in any one of a second type memory cell having a threshold characteristic and a third type memory cell having a third threshold characteristic in the active region. Location. 13. A semiconductor memory device in which a plurality of memory cells each having a gate, a gate insulating film, an active region, a source, and a drain are arranged, the semiconductor memory device comprising: a semiconductor substrate; A plurality of parallel strip-shaped bit lines for forming the source and the drain, and a plurality of parallel bit lines formed in a direction orthogonal to the bit lines for forming the gate for each memory cell above the semiconductor substrate. A strip-shaped word line, an active region is formed in a region between the source and the drain immediately below the word line, and the memory cell has the active region having a zero threshold value characteristic. 0th type memory cell, the active region has a first threshold characteristic, and the active region has a second threshold characteristic. It was the memory cells of the second class, and a semiconductor memory device that is set to any of the third class memory cells which are caused to have a third threshold characteristic in the active region. 14. The method according to claim 10, wherein the threshold value of each active region of the memory cells of each different type is set by adjusting the injection amount of program injection.
14. The semiconductor memory device according to claim 1, claim 12, or claim 13. 15. A separation band for separating active regions of different memory cells is formed in a region between adjacent word lines, and a side wall is formed on at least one side of a width direction side surface of the word line. 14. The semiconductor memory device according to claim 12, wherein the band is formed by isolation implantation using the word line and the sidewall as a mask. 16. A plurality of memory cells arranged vertically and horizontally, a plurality of connection lines connected to the plurality of memory cells and arranged in parallel in one direction, and an address for selecting the plurality of connection lines. A semiconductor memory device comprising a decoder, wherein the address decoder includes a shift register in which flip-flops connected to the connection lines are arranged in a row, and a single bus is provided to each flip-flop of the shift register. A first bus bar for inputting a clock signal, which is connected to the shift register, and a second bus bar, which is connected to each flip-flop of the shift register in a single bus system and receives at least one of a set signal and a reset signal. Semiconductor memory device. 17. A plurality of memory cells arranged vertically and horizontally, a plurality of word lines connected to the plurality of memory cells and arranged in parallel in one direction, and a plurality of word lines connected to the plurality of memory cells. A semiconductor memory device comprising: a plurality of bit lines orthogonal to a line; a first address decoder for selecting the plurality of word lines; and a second address decoder for selecting the plurality of bit lines. The first address decoder and the second address decoder include a shift register in which flip-flops respectively corresponding to the word lines or the bit lines are arranged in a row, and each flip-flop of the shift register. A first bus for inputting a clock signal, which is connected to a single bus system, and each flip-flop of the shift register, which is connected to the single bus system by a single bus system. The semiconductor memory device comprising respectively a second bus for inputting at least one of the signal and a reset signal. 18. The set input terminal of only the most advanced flip-flop of the shift register is connected to the second bus bar, and the reset input terminal of another flip-flop is connected to the second bus bar. The semiconductor memory device according to claim 16 or claim 17. 19. The semiconductor memory device according to claim 16, wherein a high-speed clock generation circuit is provided on said first bus bar. 20. The semiconductor memory device according to claim 17, wherein the shift register of the first address decoder and the shift register of the second address decoder are connected in series with each other. 21. A semiconductor memory device having a gate, a gate insulating film, an active region, a source and a drain, and arranging at least three types of memory cells of the 0th to 2nd types depending on the characteristics of the active region. A manufacturing method, comprising: forming a gate insulating film on at least a part of an upper surface of a semiconductor substrate; and forming a plurality of sources and drains for each memory cell on a part of an upper layer of the semiconductor substrate. Forming parallel strip-shaped bit lines, and selectively forming a plurality of parallel strip-shaped word lines for forming the gate for each of the memory cells on the upper surface of the gate insulating film in a direction orthogonal to the bit lines. And forming a sidewall selectively on at least one side of the width direction side surface of the word line of the second type memory cell among the plurality of word lines. A step of performing isolation implantation into the cell isolation region of the semiconductor substrate using the word lines and the sidewalls as a mask, and program implantation into the semiconductor substrate of only the 0th type memory cell among the plurality of memory cells. And a step of setting the threshold value of the active region to a value different from that of other memory cells. 22. Manufacturing of a semiconductor memory device having a gate, a gate insulating film, an active region, a source and a drain, and arranging four kinds of memory cells of the 0th to 3rd types according to the characteristics of the active region. A method for forming the gate insulating film on at least a part of an upper surface of a semiconductor substrate, and a plurality of parallel electrodes for forming the source and the drain for each memory cell on a part of an upper layer portion of the semiconductor substrate. Forming a strip-shaped bit line, and selectively forming a plurality of parallel strip-shaped word lines for forming the gate for each memory cell on the upper surface of the gate insulating film in a direction orthogonal to the bit line. A step of forming a sidewall, and selectively forming sidewalls on both sides of the word line of the third type memory cell in the width direction of the plurality of word lines, and A step of selectively forming a sidewall only on one side of a width direction side surface of a word line of the cell; a step of performing isolation implantation into a cell isolation region of the semiconductor substrate using the word line and the sidewall as a mask; 2. A method of manufacturing a semiconductor memory device, which comprises: program-injecting into a semiconductor substrate of only the 0th type memory cell among the memory cells to set a threshold value of the active region to a value different from other memory cells. 23. A semiconductor having a gate, a gate insulating film, an active region, a source and a drain, and arranging at least three kinds of memory cells of the 0th to 2nd types according to the difference in threshold characteristics of the active region. A method of manufacturing a memory device, comprising: a step of forming the gate insulating film on at least a part of an upper surface of a semiconductor substrate; and a step of selectively forming the source and the drain on a part of an upper layer portion of the semiconductor substrate for each memory cell. Forming a plurality of parallel strip-shaped word lines for forming a gate in a region immediately above the active region sandwiched between the source and the drain on the upper surface of the gate insulating film; and the word line A step of performing isolation implantation into the cell isolation region of the semiconductor substrate using the mask as a mask, and a program on the semiconductor substrate of at least some of the memory cells. Implanting and setting the threshold characteristic of each active region, wherein the step of setting the threshold characteristic masks the second type memory cells and Program injecting into the respective semiconductor substrates of the first type memory cells; masking the first type memory cells and the second type memory cells into the semiconductor substrate of the 0th type memory cells; And a program injection step. 24. A semiconductor memory having a gate, a gate insulating film, an active region, a source and a drain, and arranging four kinds of memory cells of the 0th to 3rd groups according to the difference in threshold characteristics of the active region. A method of manufacturing a device, comprising: forming the gate insulating film on at least a part of an upper surface of a semiconductor substrate; and forming the source and the drain selectively for each memory cell on a part of an upper layer portion of the semiconductor substrate. A step of forming a plurality of parallel strip-shaped word lines for forming a gate in a region immediately above the active region sandwiched between the source and the drain on the upper surface of the gate insulating film; A step of performing isolation injection into the cell isolation region of the semiconductor substrate as a mask, and a program injection into the semiconductor substrate of at least a part of the memory cells And a step of setting a threshold characteristic of each active region, wherein the step of setting the threshold characteristic masks the memory cells of the third type and the memory cells of the zeroth type and the first type. Program injecting only the memory cells of the second class and the memory cells of the second class into the semiconductor substrate, and masking the memory cells of the second class and the memory cells of the third class, and the memory of the zeroth class A program injection into each semiconductor substrate of only cells and the first type memory cells, and masking the first type memory cells, the second type memory cells, and the third type memory cells. And a program injection into the semiconductor substrate having only the 0th type memory cells. 25. A semiconductor memory device having a gate, a gate insulating film, an active region, a source and a drain, and arranging at least three types of memory cells of the 0th to 2nd types depending on the characteristics of the active region. A manufacturing method, which comprises forming the gate insulating film on at least a part of an upper surface of a semiconductor substrate, and a plurality of parallel strip-shaped word lines for forming a gate on the upper surface of the gate insulating film for each memory cell. Forming a side wall selectively on at least one side of a width direction side surface of the word line of the second type memory cell among the plurality of word lines, and forming the side wall of the word line and the side wall. Forming a source and a drain for each memory cell by diffusing impurities in a part of an upper layer of the semiconductor substrate as a mask; The method of manufacturing a semiconductor memory device and a step of setting a threshold value different from the other memory cell value of the active region and program implanted into the semiconductor substrate of only the 0 such memory cells of the Le. 26. Manufacture of a semiconductor memory device having a gate, a gate insulating film, an active region, a source and a drain, and arranging four kinds of memory cells of the 0th to 3rd types according to the characteristics of the active region. A step of forming the gate insulating film on at least a part of an upper surface of a semiconductor substrate, and a plurality of parallel strip-shaped word lines for forming a gate for each memory cell on the upper surface of the gate insulating film. Forming a sidewall selectively on both sides of the word line of the third type memory cell in the width direction of the word line of the third type memory cell, and forming a sidewall of the word line of the second type memory cell. A step of selectively forming a sidewall only on one side of the side surface in the width direction, and impurity diffusion in a part of an upper layer portion of the semiconductor substrate by using the word line and the sidewall as a mask. Forming a source and a drain for each memory cell, and programming a threshold value of the active region with a value different from that of other memory cells by performing program injection into a semiconductor substrate of only the 0th type memory cell among the plurality of memory cells. A method of manufacturing a semiconductor memory device, comprising the steps of: 27. A semiconductor having a gate, a gate insulating film, an active region, a source and a drain, and arranging at least three types of memory cells of the 0th to 2nd types according to the difference in threshold characteristics of the active region. A method of manufacturing a memory device, comprising: a step of forming the gate insulating film on at least a part of an upper surface of a semiconductor substrate; and a plurality of parallel strips for forming a gate for each memory cell on the upper surface of the gate insulating film. And forming a source line and a drain line for each memory cell by performing impurity diffusion on a part of an upper layer of the semiconductor substrate using the word line as a mask. And a step of setting a threshold characteristic of each of the active regions by program injection into a semiconductor substrate, wherein the step of setting the threshold characteristic is performed by the method of the second type. Masking the memory cells to program-inject into the respective semiconductor substrates of the 0th type memory cells and the 1st type memory cells; and mask the 1st type memory cells and the 2nd type memory cells And a program injection into the semiconductor substrate of the 0th class memory cell. 28. A semiconductor memory having a gate, a gate insulating film, an active region, a source and a drain, and arranging four kinds of memory cells of 0th to 3rd types according to a difference in threshold characteristics of the active region. A method of manufacturing a device, comprising: a step of forming the gate insulating film on at least a part of an upper surface of a semiconductor substrate; and a plurality of parallel strips for forming a gate for each memory cell on the upper surface of the gate insulating film. Forming a word line, forming a source and a drain for each memory cell by performing impurity diffusion in a part of an upper layer portion of the semiconductor substrate using the word line as a mask, and the semiconductor of at least a part of the memory cell Setting a threshold characteristic of each of the active regions by program injection into a substrate, wherein the step of setting the threshold characteristic is performed by the memory cell of the third type. Masking and performing program injection into each of the semiconductor substrates of only the 0th type memory cell, the 1st type memory cell and the 2nd type memory cell, and the 2nd type memory cell and the 2nd type memory cell. Masking the memory cells of class 3 and further performing program injection into the respective semiconductor substrates of only the memory cells of class 0 and the memory cells of class 1; the memory cells of class 1; and the class 2 Masking the memory cells of the third type and the memory cells of the third type, and further performing program injection into the semiconductor substrate of only the memory cells of the zeroth type. 29. A reference element which is provided for each of the word lines connected to each of the memory cells and sets a reference value for judging the type of each of the memory cells, and a current of the reference element and each of the memory cells. 14. The semiconductor memory device according to claim 3, claim 7, claim 12, or claim 13, further comprising a comparison circuit for comparing voltages. 30. A main bit line for supplying a current to the bit line is provided, and a plurality of memory cell current paths are formed to supply a current from the main bit line to each memory cell through the bit line. A reference bit line connected to the plurality of reference elements provided for each line is formed, and a reference current path for supplying a current from the main bit line to each memory cell through the reference bit line is formed. 30. The number of the current paths for the memory cell per one memory cell is set to be larger than the number of the current paths for the reference per one reference element.
The semiconductor memory device described. 31. A main bit line for supplying a current to the bit line is provided, and a memory cell current path is formed for supplying a current from the main bit line to each memory cell through the bit line. A reference bit line connected to the plurality of reference elements provided in the memory cell is formed, and a reference current path for supplying a current from the main bit line to each memory cell through the reference bit line is formed. The memory cell current path per memory cell and the reference current path per reference element are formed in the same number and in the same shape, and the memory cell is provided in each of the memory cell current paths. Block select transistors for memory cells that select any block of cells are connected, 30. A reference block selection transistor for selecting one of the blocks of the reference element is connected to each reference current path, and the number of block selection transistors for each current path is set to be the same as each other. Semiconductor memory device. 32. A plurality of memory cells are arranged, and a current path from the main bit line to the virtual GND line via the memory cell is formed for each memory cell, wherein the current path is the main bit. A semiconductor memory device comprising: a plurality of power source side local bit lines from a line to one of the memory cells; and a plurality of ground side local bit lines from one of the memory cells to the virtual GND line. 33. A plurality of memory cells are arranged, and for each of the memory cells, a power supply side current path from the main bit line to each of the memory cells, and a ground side from each of the memory cells to a virtual GND line. A current path is formed, and the total length of the power supply side current path and the ground side current path for each of the memory cells is set to be always constant, and the ground side current path is set to one of the virtual GND lines. In contrast, a semiconductor memory device having a plurality of ground side local bit lines.