JP5477483B2 - Nonvolatile semiconductor memory device and nonvolatile semiconductor memory device - Google Patents

Description

The present invention relates to a nonvolatile semiconductor memory device, and more particularly to a floating gate type nonvolatile semiconductor memory element (memory cell) configured by a standard CMOS process, and a nonvolatile semiconductor memory device including the nonvolatile semiconductor memory element.
This application claims priority based on Japanese Patent Application No. 2007-315113 filed in Japan on December 05, 2007 and Japanese Patent Application No. 2007-331380 filed in Japan on December 25, 2007. The contents are incorporated herein.

  BACKGROUND OF THE INVENTION Nonvolatile semiconductor memory devices represented by flash memory and EEPROM (Electrically Erasable Programmable Read Only Memory) have been used for many applications because information does not disappear even when the power is turned off. Typical examples of flash memory include NAND flash memory for large-capacity file applications, NOR flash memory used for storage control of mobile phones and the like, and typical applications of EEPROM include IC cards.

  Also, EEPROM and flash memory are used as a replacement for the mask ROM in the microcomputer because it can be rewritten at any time according to the application. Further, in recent years, an embedded type so-called logic embedded memory (embedded memory) in which a nonvolatile memory is incorporated in a part of a system LSI or logic IC has become necessary. Furthermore, a small-sized non-volatile memory of about several hundred bits to several K bits is also required as an adjustment switch that is incorporated in an analog circuit and performs tuning of a high-precision analog circuit.

  However, in a large-capacity flash memory, the memory cell can be miniaturized, but the control of the memory cell is complicated, and the area of peripheral circuits other than the memory cell including the control circuit of the memory cell becomes large and small. It was not suitable for non-volatile memories with a capacity.

Various conventional techniques have been disclosed for such nonvolatile semiconductor memory devices (see, for example, Patent Documents 1, 2, and 3).
The prior art of Patent Document 1 shows an example of the entire system of a NOR flash memory. The memory cell configuration is such that one transistor is connected in a NOR type and can be arranged at a very high density. However, if the threshold value becomes negative, the memory cell becomes defective. Writing) and controlling the threshold value of the memory cell to the positive side, the threshold control of the memory cell becomes complicated. In the prior art of Patent Document 2, an example of a complicated power supply system that mainly controls a threshold value of a memory cell is shown, mainly using a NAND flash memory as an example. The prior art in Patent Document 3 shows an example of a complicated power supply system for controlling the threshold value of a memory cell, taking a NOR flash memory as an example.

  In addition, an EEPROM composed of two transistors has a simple control circuit, but has a problem in that the memory cell becomes relatively large and the cost is increased. Furthermore, as a problem in the process structure, the conventional nonvolatile memory generally has a cell structure using two-layer polysilicon or three-layer polysilicon, and the manufacturing process is more complicated than that of the standard CMOS logic process, and the manufacturing process is more complicated. If the memory and the standard logic are simultaneously embedded in one chip, there are many manufacturing processes, yields are reduced, and the product price (cost) is increased.

  As one means for solving this problem, an EEPROM using one-layer polysilicon has been proposed (see Patent Document 4). If this one-layer polysilicon EEPROM is used, the number of manufacturing steps can be reduced as compared with the conventional two-layer polysilicon process.

  However, since the second-layer polysilicon used as the control gate is omitted, it is necessary to embed a control gate made of a diffusion layer under the floating gate, which is more complicated than the standard CMOS process used in logic. turn into. Furthermore, if the diffusion layer embedded at a high concentration is oxidized, an oxide film of poor quality is formed, and the probability of occurrence of a defect is high, and reliability is also a problem.

JP 2002-133878 A JP 2000-1000018 A Japanese Patent Laid-Open No. 2001-210086 JP-A-10-289959

  As described above, in the conventional nonvolatile semiconductor memory device, when the charge accumulated in the floating gate in the nonvolatile semiconductor memory element (memory cell) is erased, the threshold value of the memory cell is controlled to be positive. A complicated control circuit is necessary for this purpose. Conventionally, a method of erasing charges by a tunnel current by Fowler-Nordheim is mainly used. In this method, a threshold value between a memory cell and a source is controlled to a predetermined positive value. This is because it is difficult. In order to realize an EEPROM using single-layer polysilicon, a manufacturing process that is more complicated than a standard CMOS process is required.

The present invention has been made in view of such circumstances, and an object of the present invention is to eliminate a memory cell without using a complicated control circuit when erasing accumulated charges in a memory cell of a nonvolatile semiconductor memory device. It is an object to provide a non-volatile semiconductor memory device and a non-volatile semiconductor memory device that can be controlled to be positive and can be manufactured by a standard CMOS process.
Another object of the present invention is to easily store and erase charges in a floating gate of a nonvolatile semiconductor memory element (memory cell) constituting a nonvolatile semiconductor memory device, and to store charges stored in the floating gate. Can be easily controlled using a floating gate made of single-layer polysilicon, and a nonvolatile semiconductor memory device including this nonvolatile semiconductor memory device A semiconductor memory device is provided.

The present invention has been made to solve the above problems, and one embodiment of the present invention includes a floating gate disposed on an FET formed on a semiconductor substrate, and a control gate for applying a gate voltage to the floating gate. A floating gate type nonvolatile semiconductor memory device comprising a source and a drain, wherein a first low voltage is applied to the control gate and a first high voltage is applied to the drain during charge accumulation in the floating gate. Or a first low voltage is applied to the control gate, a first high voltage is applied to the source, and hot electrons due to band-to-band are generated in the semiconductor substrate. The charge is injected into the floating gate and accumulated, and the flow A second low voltage is applied to the control gate and a second high voltage is applied to the drain, or a second low voltage is applied to the control gate when erasing the charge accumulated in the storage gate. A second high voltage is applied to the source to generate a band-to-band hot hole in the semiconductor substrate, and the charge accumulated in the floating gate is erased by the hot hole, The first high voltage is higher than the second high voltage, and the first low voltage is higher than the second low voltage (second low voltage <first low voltage <second high voltage <second 1), the absolute value of the first high voltage is greater than the absolute value of the first low voltage, and the absolute value of the second high voltage is greater than the absolute value of the second low voltage ( | First low voltage | <| 1, high voltage |, | second low voltage | <| second high voltage |), the second low voltage is a negative low voltage, and the charge accumulated in the floating gate is erased. A non-volatile semiconductor memory device that controls a negative threshold between the control gate and the source by applying a negative low voltage to the control gate.
The first aspect of the present invention, a floating gate disposed on FET formed on a semiconductor substrate, a nonvolatile semiconductor 1 transistor structure of the floating gate type comprising a control gate providing a gate voltage to the floating gate The present invention relates to a memory element. In this nonvolatile semiconductor memory device, a voltage is applied to the control gate to cause a current to flow between the source and the drain, and charges generated in the channel are injected and stored in the floating gate. The nonvolatile semiconductor memory device applies a voltage between the floating gate and the drain or between the floating gate and the source at the time of erasing the electric charge stored in the floating gate, and performs band-to-band (Band to Band). ) Is generated in the semiconductor substrate, and charges accumulated in the floating gate are erased by the hot holes.
In this case, in a non-volatile semiconductor memory element (memory cell) having a floating gate type single transistor (FET (Field effect transistor)) structure, for example, when erasing charges accumulated in the floating gate, a voltage is applied between the floating gate and the drain. To generate hot holes in the semiconductor substrate by band-to-band (Band to Band), and erase the charges accumulated in the floating gate by the hot holes.
Thus, unlike the conventional method for erasing the floating gate charge by the tunnel current, the floating gate charge can be erased while keeping the threshold value between the control gate and the source of the memory cell on the positive side. Further, in the charge erasing method using hot holes, the threshold value can be controlled only by controlling the voltage of the control gate, so that complicated control is not required. In addition, since complicated control by the control circuit is not required, even when a non-volatile memory such as an EEPROM according to the present invention and standard logic are simultaneously embedded in one chip, the yield is reduced and the price of the product ( Cost) is reduced.

When erasing the charge accumulated in the floating gate by the hot hole, by applying a positive bias to the control gate, the control gate and the source are controlled to have a positive threshold. Also good.
In this case, when the charge accumulated in the floating gate is erased by hot holes, a bias voltage is applied to the control gate so as to have a positive threshold between the control gate and the source.
This makes it possible to control the threshold between the control gate and the source of the memory cell to be on the positive side by applying a bias voltage to the control gate, unlike the conventional method for erasing the charge of the floating gate by the tunnel current. The charge of the floating gate can be erased. Further, since the threshold value can be controlled only by controlling the voltage of the control gate, complicated control is not required. In addition, since complicated control by the control circuit is not required, even when a non-volatile memory such as an EEPROM according to the present invention and standard logic are simultaneously embedded in one chip, the yield is reduced and the price of the product ( Cost) is reduced.

According to a second aspect of the present invention, there is provided a floating gate type non-volatile semiconductor memory device having a floating gate disposed on an FET formed on a semiconductor substrate and a control gate for applying a gate voltage to the floating gate. The present invention relates to a nonvolatile semiconductor memory device configured by arranging a plurality of semiconductor memory devices. In this nonvolatile semiconductor memory device, a voltage is applied to the control gate to cause a current to flow between the source and the drain, and the charge generated in the channel is injected and stored in the floating gate, and is stored in the floating gate. At the time of charge erasing, a voltage is applied between the floating gate and the drain or between the floating gate and the source to generate a band-to-band hot hole in the semiconductor substrate. The charge accumulated in the floating gate is erased. The nonvolatile semiconductor memory device further applies a positive bias to the control gate so as to have a positive threshold between the control gate and the source when erasing the electric charge stored in the floating gate.
In this case, in a non-volatile semiconductor memory device in which a plurality of non-volatile semiconductor memory elements (memory cells) having a floating gate type 1 transistor (FET) configuration are arranged, in each memory cell, at the time of erasing charges accumulated in the floating gate, For example, a voltage is applied between the floating gate and the drain to generate a band-to-band hot hole in the semiconductor substrate, and the charge accumulated in the floating gate is erased by the hot hole. In addition, when erasing the charge accumulated in the floating gate by hot holes, a bias voltage is applied to the control gate so that a positive threshold value is provided between the control gate and the source.
As a result, in each memory cell in the nonvolatile semiconductor memory device, the threshold voltage between the control gate and the source of the memory cell is controlled to be on the positive side only by applying a bias voltage to the control gate. The charge can be erased. In addition, since complicated control by the control circuit is not required, even when a non-volatile memory such as an EEPROM according to the present invention and standard logic are simultaneously embedded in one chip, the yield is reduced and the price of the product ( Cost) is reduced.

For each non-volatile semiconductor memory element in the non-volatile semiconductor memory device, when erasing the charge accumulated in the floating gate, the control gate of the selected non-volatile semiconductor memory element has a positive threshold value when erasing the charge. A first bias voltage for applying may be applied, and a second bias voltage for suppressing the generation of the hot holes may be applied to a control gate of a non-selected nonvolatile semiconductor memory element.
In this case, for a nonvolatile semiconductor memory element (memory cell) that attempts to erase the charge accumulated in the floating gate, a first bias voltage (for providing a positive threshold when erasing the charge in the floating gate) For example, 1v) is applied. For a memory cell that does not erase charges accumulated in the floating gate, a second bias voltage (for example, 4v) is applied to the second bias voltage control gate for suppressing the generation of hot holes.
Thus, when a common voltage (for example, 7v) is applied to the drain or source of each memory cell, the memory cell that erases the charge by generating a hot hole and the memory that does not erase the charge without generating the hot hole The cell can be selected by a bias voltage applied to the control gate.

The second bias voltage may be higher than the first bias voltage.
In this case, a first bias voltage (for example, 1 v) is applied to the control gate for a nonvolatile semiconductor memory element (memory cell) that attempts to erase charges accumulated in the floating gate. A second bias voltage (for example, 4 v) is applied to the control gate for a memory cell that does not erase charges accumulated in the floating gate. Thus, the second bias voltage is set higher than the first bias voltage.
As a result, by selecting the level of voltage applied to the control gate of each memory cell, a memory cell that erases charges by generating hot holes and a memory cell that does not erase charges without generating hot holes are selected. can do.

A third aspect of the present invention relates to a floating gate type non-volatile semiconductor memory device including a single-layer polysilicon floating gate on an FET configured by a standard CMOS process. The nonvolatile semiconductor memory device includes a control gate that applies a gate voltage to the floating gate, and a voltage is applied to the control gate to cause a current to flow between the source and the drain to inject charges generated in the channel into the floating gate. A plurality of non-volatile semiconductor memory elements to be stored are arranged. In this nonvolatile semiconductor memory device, the nonvolatile semiconductor memory element applies a voltage between the floating gate and the drain or between the floating gate and the source when erasing charges accumulated in the floating gate, A hot hole due to band-to-band is generated in the semiconductor substrate, and charges accumulated in the floating gate are erased by the hot hole.
In this case, in a non-volatile semiconductor memory device including a floating gate type non-volatile semiconductor memory element (memory cell) including a single-layer polysilicon floating gate on an FET configured by a standard CMOS process, each memory cell has a floating state. At the time of erasing the charge accumulated in the gate, for example, a voltage is applied between the floating gate and the drain to generate a hot hole due to band-to-band in the semiconductor substrate. Erase the accumulated charge.
As a result, in a nonvolatile semiconductor memory device having a single-layer polysilicon floating gate type memory cell, the threshold value between the control gate and the source of the memory cell is set to a positive value, unlike the conventional method for erasing the floating gate charge by a tunnel current. The charge on the floating gate can be erased while being on the side. Further, in the charge erasing method using hot holes, the threshold value can be controlled only by controlling the voltage of the control gate, so that complicated control is not required. In addition, since complicated control by the control circuit is not required, even when a non-volatile memory such as an EEPROM according to the present invention and standard logic are simultaneously embedded in one chip, the yield is reduced and the price of the product ( Cost) is reduced.

A positive bias may be applied to the control gate so as to have a positive threshold between the control gate and the source when erasing the electric charge stored in the floating gate.
In this case, in the nonvolatile semiconductor memory device including the single-layer polysilicon floating gate type nonvolatile semiconductor memory element (memory cell), when erasing the charge accumulated in the floating gate in the memory cell by hot holes, By applying a bias voltage to the control gate, control is performed so as to have a positive threshold between the control gate and the source.
As a result, in the memory cell in the nonvolatile semiconductor memory device, unlike the conventional method for erasing the charge of the floating gate by the tunnel current, by applying a bias voltage to the control gate, the memory cell is controlled between the control gate and the source. The charge on the floating gate can be erased while keeping the threshold value on the positive side. Further, since the threshold value can be controlled only by controlling the voltage of the control gate, complicated control is not required. In addition, since complicated control by the control circuit is not required, even when a non-volatile memory such as an EEPROM according to the present invention and standard logic are simultaneously embedded in one chip, the yield is reduced and the price of the product ( Cost) is reduced.

When erasing charges accumulated in the floating gate, a first bias voltage is applied to the control gate of the selected nonvolatile semiconductor memory element to give a positive threshold value when erasing the charges. A second bias voltage for suppressing the generation of the hot hole may be applied to the control gate of the conductive semiconductor memory element.
In this case, in a non-volatile semiconductor memory device having a single-layer polysilicon floating gate type non-volatile semiconductor memory element (memory cell), a memory cell intended to erase charges accumulated in the floating gate in the memory cell Thus, a first bias voltage (for example, 1 v) is applied to the control gate. A second bias voltage (for example, 4 v) is applied to the control gate for a memory cell that does not erase charges accumulated in the floating gate.
Thus, when a common voltage (for example, 7v) is applied to the drain or source of each memory cell, the memory cell that erases the charge by generating a hot hole and the memory that does not erase the charge without generating the hot hole The cell can be selected by a bias voltage applied to the control gate.

A fourth aspect of the present invention has a two-layer polysilicon gate structure of a first-layer polysilicon floating gate and a second-layer polysilicon control gate for applying a voltage to the floating gate, and the control gate. The present invention relates to a non-volatile semiconductor memory device configured by arranging a plurality of non-volatile semiconductor memory elements for applying a voltage to the source and flowing current between the source and drain and injecting and accumulating charges generated in the channel into the floating gate. . The nonvolatile semiconductor memory device applies a voltage between the floating gate and the drain or between the floating gate and the source at the time of erasing the electric charge accumulated in the floating gate, and is based on band-to-band. Hot holes are generated in the semiconductor substrate, and charges accumulated in the floating gate are erased by the hot holes.
In this case, in a nonvolatile semiconductor memory device including a floating gate type nonvolatile semiconductor memory element (memory cell) having a two-layer polysilicon gate structure, in each memory cell, when erasing charges accumulated in the floating gate, for example, A voltage is applied between the floating gate and the drain to generate a band-to-band hot hole in the semiconductor substrate, and the charge accumulated in the floating gate is erased by the hot hole.
As a result, in the nonvolatile semiconductor memory device having the two-layer polysilicon gate structure, the threshold value between the control gate and the source of the memory cell is set to the positive side, unlike the conventional method for erasing the floating gate charge by the tunnel current. The charge of the floating gate can be erased. Further, in the charge erasing method using hot holes, the threshold value can be controlled only by controlling the voltage of the control gate, so that complicated control is not required. In addition, since complicated control by the control circuit is not required, even when a non-volatile memory such as an EEPROM according to the present invention and standard logic are simultaneously embedded in one chip, the yield is reduced and the price of the product ( Cost) is reduced.

A positive bias may be applied to the control gate so as to have a positive threshold between the control gate and the source when erasing the electric charge stored in the floating gate.
In this case, in a nonvolatile semiconductor memory device having a floating gate type nonvolatile semiconductor memory element (memory cell) having a two-layer polysilicon gate structure, when charges accumulated in the floating gate in the memory cell are erased by hot holes In addition, by applying a bias voltage to the control gate, control is performed so as to have a positive threshold between the control gate and the source.
Thus, unlike a conventional method for erasing the charge of the floating gate by a tunnel current in a memory cell having a two-layer polysilicon gate structure, by applying a bias voltage to the control gate, the memory cell is controlled between the control gate and the source. The charge on the floating gate can be erased while keeping the threshold value on the positive side. Further, since the threshold value can be controlled only by controlling the voltage of the control gate, complicated control is not required. In addition, since complicated control by the control circuit is not required, even when a non-volatile memory such as an EEPROM according to the present invention and standard logic are simultaneously embedded in one chip, the yield is reduced and the price of the product ( Cost) is reduced.

When erasing charges accumulated in the floating gate, a first bias voltage is applied to the control gate of the selected nonvolatile semiconductor memory element to give a positive threshold value when erasing the charges. A second bias voltage for suppressing the generation of the hot hole may be applied to the control gate of the conductive semiconductor memory element.
In this case, in a non-volatile semiconductor memory device including a floating gate type non-volatile semiconductor memory element (memory cell) having a two-layer polysilicon gate structure, a memory cell intended to erase charges accumulated in the floating gate in the memory cell For this, a first bias voltage (for example, 1 v) is applied to the control gate. A second bias voltage (for example, 4 v) is applied to the control gate for a memory cell that does not erase charges accumulated in the floating gate.
Accordingly, in a memory cell having a two-layer polysilicon gate structure, when a common voltage (for example, 7 v) is applied to the drain or source of each memory cell, a memory cell that generates a hot hole and erases the charge; A memory cell that does not erase a charge without generating a hot hole can be selected by a bias voltage applied to the control gate.

According to a fifth aspect of the present invention, there is provided a floating gate disposed on an FET formed on a semiconductor substrate, and a control gate for applying a gate voltage to the floating gate, and a source / drain is applied by applying a voltage to the control gate. Each memory cell, which is a non-volatile semiconductor memory element that accumulates electric charge by injecting electric charge generated in the channel by flowing current between them into the floating gate, is arranged in a matrix at the intersection of the word line and the data line The present invention relates to a nonvolatile semiconductor memory device. The memory cell applies a voltage between the floating gate and the drain or between the floating gate and the source at the time of erasing the electric charge accumulated in the floating gate, and generates a hot hole between bands and bands (Band to Band). It is configured to erase the charge generated in the semiconductor substrate and accumulated in the floating gate by the hot hole, and between the control gate and the source when erasing the charge accumulated in the floating gate. The control gate is configured to apply a positive bias so as to have a positive threshold. The memory cell further has a control gate of the memory cell connected to a corresponding word line, a drain of the memory cell connected to a corresponding data line, a source of the memory cells connected in common, and the common The connected source line is connected to a source control circuit that applies a desired bias voltage to the source.
In this case, in the nonvolatile semiconductor memory device in which a plurality of floating gate type nonvolatile semiconductor memory elements (memory cells) are arranged, in each memory cell, when erasing charges accumulated in the floating gate, for example, between the floating gate and the drain A voltage is applied to the semiconductor substrate to generate a hot hole by band-to-band in the semiconductor substrate, and the charge accumulated in the floating gate is erased by the hot hole. In addition, when erasing the charge accumulated in the floating gate by hot holes, a bias voltage is applied to the control gate so that a positive threshold value is provided between the control gate and the source. Further, the control gate of the memory cell is connected to the corresponding word line, the drain is connected to the corresponding data line, the source is connected in common, and the commonly connected source line is connected to the source at a desired voltage. To be connected to a source control circuit for applying.
Thus, by applying a desired bias voltage to the word line, the data line, and the source line, a desired memory cell can be selected and the charge accumulated in the floating gate can be erased.

The non-volatile semiconductor memory device has a collective erase mode for simultaneously erasing charges of all memory cells as an operation mode for erasing the accumulated charges by applying a bias voltage necessary for generating the hot holes from the drain side. A page erase mode for erasing only the charge of the memory cell connected to the selected word line and a bit erase mode for erasing the charge of only one selected memory cell are configured. In the batch erase mode, a bias voltage A is applied to all the word lines to give a positive threshold when erasing charges in the memory cell, and it is necessary to generate the hot holes for all the data lines. And a bias voltage C for turning off the memory cell is applied (bias voltage A <bias voltage C <bias voltage). B) In the page erase mode, a bias voltage A is applied to a desired word line to give a positive threshold when erasing charges in the memory cell selected by the word line, and the other word lines are applied. A bias voltage D for suppressing the generation of the hot holes is applied, and a bias voltage B necessary for generating the hot holes is applied to all the data lines. In addition, a bias voltage D for opening the commonly connected source of the memory cells or turning off the memory cells is applied (bias voltage A <bias voltage D <bias voltage B). . In the bit erase mode, a bias voltage A is applied to a desired word line to give a positive threshold when erasing charges in the memory cell selected by the word line, and the other word lines are A bias voltage D for suppressing the generation of hot holes is applied, a bias voltage B necessary for generating the hot holes is applied to a memory cell selected by the data line with respect to a desired data line, and other data A bias voltage D is applied to open the line or to turn off the memory cell, and to open a commonly connected source of the nonvolatile semiconductor memory element or to turn off the memory cell. The voltage D may be applied.
In this case, the charge of the floating gate in the memory cell can be erased from the drain side. In this case, in the batch erase mode, a bias voltage A (for example, 1 v) for applying a positive threshold to the memory cells is applied to all the word lines, and it is necessary to generate hot holes for all the data lines. A positive bias voltage B (for example, 7v) is applied, and the commonly connected sources are opened. In the page erase mode, a bias voltage A (for example, 1v) for applying a positive threshold value to a memory cell selected by a word line is applied to suppress the occurrence of hot holes with respect to other word lines. A bias voltage D (for example, 4v) is applied, a bias voltage B (for example, 7v) necessary for generating hot holes is applied to all the data lines, and the commonly connected sources of the memory cells are opened. In the bit erase mode, a bias voltage A (for example, 1 v) for applying a positive threshold is applied to the memory cell selected by the word line to suppress the generation of hot holes for other word lines. A bias voltage D (for example, 4v) is applied, a bias voltage B (for example, 7v) necessary for generating hot holes is applied to the memory cell selected by the data line, and the other data lines are opened. , Open the commonly connected source.
As a result, by applying a desired bias voltage to the word line, data line, and commonly connected source line, a desired memory cell is selected, and memory cell batch erase, page erase, and bit erase are performed on the drain side. Can be done from.

The nonvolatile semiconductor memory device has a collective erasure mode in which charges of all memory cells are erased simultaneously as an operation mode in which a bias voltage necessary for generating the hot holes is applied from the source side to erase the accumulated charges. And a page erase mode for erasing only the charges of the memory cells connected to the selected word line. In the batch erase mode, a bias voltage A is applied to all of the word lines to give a positive threshold when erasing charges in the memory cell, and all of the data lines are opened, or A bias voltage C for turning off the memory cell is applied, and a bias voltage B necessary for generating the hot hole is applied to the commonly connected sources (bias voltage A <bias voltage C <bias voltage). B). In the page erase mode, a bias voltage A is applied to a desired word line to give a positive threshold when erasing charges in the memory cell selected by the word line, and to other word lines. The bias voltage D for suppressing the occurrence of the hot hole is applied and all the data lines are opened, or the bias voltage D for turning off the memory cell is applied, and the common connection A bias voltage B necessary for generating the hot hole may be applied to the source (bias voltage A <bias voltage D <bias voltage B).
In this case, the charge of the floating gate in the memory cell can be erased from the source side. In this case, in the batch erase mode, a bias voltage A (for example, 1 v) for applying a positive threshold value to the memory cells is applied to all of the word lines, all of the data lines are opened and commonly connected. A bias voltage B (for example, 7v) necessary for generating hot holes is applied to the source. In the page erase mode, a bias voltage A (for example, 1 v) for applying a positive threshold value to the memory cell selected by the word line is applied to suppress the occurrence of hot holes with respect to other word lines. A bias voltage D (for example, 4v) is applied, all the data lines are opened, and a bias voltage B (for example, 7v) necessary for generating hot holes is applied to the commonly connected sources.
Thus, by applying a desired bias voltage to the word line, the data line, and the commonly connected source line, a desired memory cell can be selected, and batch erase and page erase of the memory cell can be performed from the source side. it can. For this reason, there is no possibility of deteriorating the oxide film on the drain side.

The non-volatile semiconductor memory device may be a floating gate type non-volatile semiconductor memory device including a single-layer polysilicon floating gate on an FET configured by a standard CMOS process.
Thus, in a non-volatile semiconductor memory device having a single-layer polysilicon floating gate type memory cell, a desired bias voltage is applied to a word line, a data line, and a commonly connected source line to thereby form a desired memory. A cell can be selected to erase the charge stored in the floating gate.

The nonvolatile semiconductor memory device may have a two-layer polysilicon gate structure of a first-layer polysilicon floating gate and a second-layer polysilicon control gate for applying a voltage to the floating gate.
Thus, in a nonvolatile semiconductor memory device including a memory cell having a two-layer polysilicon gate structure, a desired bias voltage is applied to a word line, a data line, and a commonly connected source line to thereby form a desired memory cell. By selecting, the charge accumulated in the floating gate can be erased.

According to a sixth aspect of the present invention, there is provided a floating gate disposed on an FET formed on a semiconductor substrate, and a control gate for applying a gate voltage to the floating gate. Each memory cell, which is a non-volatile semiconductor memory element that accumulates electric charge by injecting electric charge generated in the channel by flowing current between them into the floating gate, is arranged in a matrix at the intersection of the word line and the data line The present invention relates to a nonvolatile semiconductor memory device. The memory cell applies a voltage between the floating gate and the drain or between the floating gate and the source at the time of erasing the electric charge accumulated in the floating gate, and generates a hot hole between bands and bands (Band to Band). It is configured to erase the charge generated in the semiconductor substrate and accumulated in the floating gate by the hot hole, and between the control gate and the source when erasing the charge accumulated in the floating gate. The control gate is configured to apply a positive bias so as to have a positive threshold. Further, the control gate of the memory cell is connected to the corresponding word line, the drain of the memory cell is connected to the corresponding data line, and the source of each memory cell is corresponding to the data line arranged in parallel with the data line. Connected to source line.
In this case, in the nonvolatile semiconductor memory device in which a plurality of floating gate type nonvolatile semiconductor memory elements (memory cells) are arranged, in each memory cell, when erasing charges accumulated in the floating gate, for example, between the floating gate and the source A voltage is applied to the semiconductor substrate to generate a hot hole by band-to-band in the semiconductor substrate, and the charge accumulated in the floating gate is erased by the hot hole. In addition, when erasing the charge accumulated in the floating gate by hot holes, a bias voltage is applied to the control gate so that a positive threshold value is provided between the control gate and the source. Further, the control gate of the memory cell is connected to the corresponding word line, the drain is connected to the corresponding data line, and the source is connected to the corresponding source line.
Thus, by applying a desired bias voltage to the word line, the data line, and the source line, a desired memory cell can be selected and the charge accumulated in the floating gate can be erased. In particular, since the charge of the floating gate can be erased from the source side, there is no possibility of deteriorating the oxide film on the drain side.

The nonvolatile semiconductor memory device has a collective erasure mode in which charges of all memory cells are erased simultaneously as an operation mode in which a bias voltage necessary for generating the hot holes is applied from the source side to erase the accumulated charges. A page erase mode for erasing only the charge of the memory cell connected to the selected word line and a bit erase mode for erasing the charge of only one selected memory cell are configured. In the batch erase mode, a bias voltage A is applied to all of the word lines to give a positive threshold when erasing charges in the memory cells, all of the data lines are opened, and the source lines A bias voltage B necessary for generating the hot hole is applied to all of them (bias voltage A <bias voltage B). In the page erase mode, a bias voltage A is applied to a desired word line to give a positive threshold when erasing charges in the memory cell selected by the word line, and to other word lines. A bias voltage D for suppressing the occurrence of the hot holes is applied, all the data lines are opened, and a bias voltage B necessary for the generation of the hot holes is applied to all the source lines (bias Voltage A <bias voltage D <bias voltage B). In the bit erase mode, a bias voltage A is applied to a desired word line to give a positive threshold when erasing charges in the memory cell selected by the word line, and to other word lines. A bias voltage D for suppressing the occurrence of the hot hole is applied, all the data lines are opened, a bias voltage B necessary for the generation of the hot hole is applied to a desired source line, The source line is opened (bias voltage A <bias voltage D <bias voltage B).
In this case, batch erase, page erase, and bit erase are performed from the source side in the charge erase mode in the memory cell. In this case, in the batch erase mode, a bias voltage A (for example, 1 v) for applying a positive threshold value to the memory cells is applied to all of the word lines, all of the data lines are opened, and all of the source lines are opened. A bias voltage B (for example, 7v) necessary for generating hot holes is applied. In the page erase mode, a bias voltage A (for example, 1v) for applying a positive threshold value to a memory cell selected by a word line is applied to suppress the occurrence of hot holes with respect to other word lines. A bias voltage D (for example, 4v) is applied, all of the data lines are opened, and a bias voltage B (for example, 7v) necessary for generating hot holes is applied to all of the source lines. In the bit erase mode, a bias voltage A (for example, 1 v) for applying a positive threshold value to the memory cell selected by the word line is applied to suppress the occurrence of hot holes with respect to other word lines. A bias voltage D (for example, 4v) is applied, all the data lines are opened, a bias voltage B (for example, 7v) necessary for generating hot holes is applied to a desired source line, and other sources Open the line.
Thus, batch erase, page erase, and bit erase can be performed from the source side in the charge erase mode in the memory cell. In particular, since the charge of the floating gate can be erased from the source side, there is no possibility of deteriorating the oxide film on the drain side.

The non-volatile semiconductor memory device may be a floating gate type non-volatile semiconductor memory device including a single-layer polysilicon floating gate on an FET configured by a standard CMOS process.
As a result, in a nonvolatile semiconductor memory device having a single-layer polysilicon floating gate type memory cell, when erasing charges in the memory cell, batch erasing, page erasing, and bit erasing can be performed from the source side. it can. In particular, since the charge of the floating gate can be erased from the source side, there is no possibility of deteriorating the oxide film on the drain side.

A two-layer polysilicon gate structure of a first-layer polysilicon floating gate and a second-layer polysilicon control gate for applying a voltage to the floating gate may be provided.
Thus, in a nonvolatile semiconductor memory device having a memory cell having a two-layer polysilicon gate structure, batch erase, page erase, and bit erase can be performed from the source side when erasing charges in the memory cell. In particular, since the charge of the floating gate can be erased from the source side, there is no possibility of deteriorating the oxide film on the drain side.

According to a seventh aspect of the present invention, there is provided a floating gate type nonvolatile semiconductor memory comprising a floating gate disposed on an FET formed on a semiconductor substrate, a control gate for applying a gate voltage to the floating gate, and a source and a drain. It relates to an element. In this volatile semiconductor memory device, the first low voltage is applied to the control gate and the first high voltage is applied to the drain when the electric charge is accumulated in the floating gate, or the first high voltage is applied to the control gate. A low voltage of 1 is applied, a first high voltage is applied to the source, hot electrons due to band-to-band (Band to Band) are generated in the semiconductor substrate, and charge is injected and accumulated in the floating gate. And at the time of erasing the charge accumulated in the floating gate, a second low voltage is applied to the control gate and a second high voltage is applied to the drain, or a second low voltage is applied to the control gate. A voltage is applied, a second high voltage is applied to the source, and band-to-band Hot holes are generated in the semiconductor substrate, and charges accumulated in the floating gate are erased by the hot holes.
In this case, a floating gate type transistor (FET (Field effect trans
in a non-volatile semiconductor memory device (memory cell) configured by istor)), for example, a voltage is applied between the floating gate and the drain when the charge is accumulated in the floating gate, and the band-to-band (Band to Band) Hot electrons are generated in the semiconductor substrate, and charges are injected into the floating gate by the hot electrons. Further, when erasing charges accumulated in the floating gate, for example, a voltage is applied between the floating gate and the drain to generate a hot hole by band-to-band in the semiconductor substrate. The charge accumulated in the floating gate is erased. Thus, in the present invention, charge injection into the floating gate and charge erasure are performed by the same band-to-band control method. In addition, when erasing the charge of the floating gate, unlike the conventional method of erasing the charge of the floating gate by the tunnel current, while controlling the threshold value between the control gate and the source of the memory cell to a desired value, Erase the charge.
As a result, accumulation and erasure of charges in the floating gate can be performed by controlling the voltage applied between the drain (or source) and the control gate, and a complicated control circuit is not required. Further, it can be manufactured by a standard CMOS process. Furthermore, since a complicated control circuit is not required, even when a non-volatile memory such as an EEPROM according to the present invention and standard logic are embedded in one chip at the same time, a decrease in yield is reduced and the price of the product (cost) is reduced. ).

The first high voltage is higher than the second high voltage, and the first low voltage is higher than the second low voltage (second low voltage <first low voltage <second high voltage < (First high voltage).
In the non-volatile semiconductor memory device of the present invention having the above-described configuration, at the time of charge accumulation in the floating gate, for example, the source is opened and the first low voltage (3v) is applied to the control gate and the first high voltage is applied to the drain. A voltage (9v) is applied, hot electrons due to band-to-band (Band to Band) are generated in the semiconductor substrate, and charges are injected and accumulated in the floating gate. When erasing charges accumulated in the floating gate, for example, the source is opened, the second low voltage (−1 to 0 v) is applied to the control gate, and the second high voltage (7 v) is applied to the drain. Hot holes due to band-to-band are generated in the semiconductor substrate, and charges accumulated in the floating gate are erased by the hot holes.
Thereby, injection of charge into the floating gate and erasure of the accumulated charge can be easily performed only by controlling the voltage applied to the control gate and the drain (or source). Further, the threshold between the control gate and the source can be controlled to a desired value at the time of erasing the electric charge from the floating gate.

The second low voltage is negative, and a negative threshold is applied between the control gate and the source by applying a negative voltage to the control gate when erasing the charge accumulated in the floating gate. You may control to have.
In this case, since the negative voltage is applied to the control gate when erasing the charge accumulated in the floating gate, the threshold between the control gate and the source can be controlled to be a negative value. That is, in the nonvolatile semiconductor memory element of the present invention, by controlling the voltage applied to the control gate, the threshold value can be controlled to both the positive side and the negative side, and the data written to the memory cell can be clearly distinguished.

The nonvolatile semiconductor memory device may have a one-layer polysilicon floating gate.
As a result, in a nonvolatile semiconductor memory device having a floating gate having a single-layer polysilicon structure, charge is injected into and accumulated in the floating gate only by controlling the voltage applied to the control gate and drain (or source). It is possible to easily erase the charges. Further, the threshold between the control gate and the source can be controlled to a desired value at the time of erasing the electric charge from the floating gate.

According to an eighth aspect of the present invention, there is provided a floating gate type nonvolatile semiconductor memory comprising a floating gate disposed on an FET formed on a semiconductor substrate, a control gate for applying a gate voltage to the floating gate, and a source and a drain. The present invention relates to a nonvolatile semiconductor memory device configured by arranging a plurality of elements. The non-volatile semiconductor memory device applies a first low voltage to the control gate and a first high voltage to the source during charge accumulation in the floating gate, and a band-to-band (Band to Band) ) Is generated in the semiconductor substrate to inject and accumulate charges in the floating gate, and a second low voltage is applied to the control gate when erasing the charges accumulated in the floating gate. A second high voltage is applied to the source, a hot hole due to band-to-band is generated in the semiconductor substrate, and the charge accumulated in the floating gate is erased by the hot hole. (Second low voltage <first low voltage <second high voltage <first In addition, the second low voltage of a predetermined value is applied to the control gate so as to have a predetermined threshold between the control gate and the source when erasing the electric charge stored in the floating gate. Apply.
In this case, in the nonvolatile semiconductor memory device in which a plurality of floating gate type nonvolatile semiconductor memory elements (memory cells) are arranged, in each memory cell, a voltage is applied between the control gate and the source when charge is accumulated in the floating gate. Then, hot electrons are generated by band-to-band, and the hot electrons are injected into the floating gate and accumulated. Further, when erasing charges, a voltage is applied between the control gate and the source to generate hot holes between bands, and the charges accumulated in the floating gate are erased by the hot holes.
As a result, in the memory cell in the nonvolatile semiconductor memory device, accumulation and erasure of charges in the floating gate can be performed by controlling the voltage applied between the drain (or source) and the control gate, and the complicated No control circuit is required. In addition, since a complicated control circuit is not required, even when a non-volatile memory such as an EEPROM according to the present invention and standard logic are simultaneously embedded in one chip, the yield reduction is reduced and the product price (cost) is reduced. ).

A ninth aspect of the present invention is a nonvolatile semiconductor memory device comprising a first nonvolatile semiconductor memory element and a second nonvolatile semiconductor memory element, wherein the first and second nonvolatile semiconductor memory elements are The floating gate type nonvolatile semiconductor memory device includes a floating gate disposed on an FET formed on a semiconductor substrate, a control gate for applying a gate voltage to the floating gate, and a source and a drain. The nonvolatile semiconductor memory device applies a first low voltage to the control gate and a first high voltage to the source when the electric charge is accumulated in the floating gate, and a band-to-band (Band to Band) ) Is generated in the semiconductor substrate to inject and accumulate charges in the floating gate, and a second low voltage is applied to the control gate when erasing the charges accumulated in the floating gate. A second high voltage is applied to the source, a hot hole due to band-to-band is generated in the semiconductor substrate, and the charge accumulated in the floating gate is erased by the hot hole. (Second low voltage <first low voltage <second high voltage <first high voltage Pressure). In the nonvolatile semiconductor memory device, the source of the first nonvolatile semiconductor memory element and the source of the second nonvolatile semiconductor memory element are commonly connected, and the drain of the first nonvolatile semiconductor memory element is When reading data from the first and second nonvolatile semiconductor memory elements connected to the first transfer gate and connected to the drain of the second nonvolatile semiconductor memory element and the second transfer gate. A predetermined gate voltage is applied to each of the control gate of the first nonvolatile semiconductor memory element and the control gate of the second nonvolatile semiconductor memory element, and the first and second nonvolatile semiconductor memories are applied. An output signal from the drain of the element is read by turning on the transfer gate.
In this case, two non-volatile semiconductor memory elements are provided as memory cells, and this memory cell applies a voltage between the control gate and the source during the charge accumulation in the floating gate, and the band-to-band. The hot electrons are generated and injected into the floating gate and accumulated. Further, when erasing charges, a voltage is applied between the control gate and the source to generate hot holes between bands, and the charges accumulated in the floating gate are erased by the hot holes. The sources of the two memory cells are connected in common, and the drains are connected to the transfer gates. When reading data from the memory cell, a predetermined gate voltage is applied to the control gate of each memory cell, and the transfer gate is turned on to read data from the memory cell.
As a result, a memory is configured using two nonvolatile semiconductor memory elements (memory cells) of the present invention, and a positive logic signal of data held in the memory and an inverted logic signal of the data can be output independently.

The nonvolatile semiconductor memory device includes an SRAM (Static Random Access Memory) that holds a signal by a flip-flop circuit, and outputs an output signal from the first and second nonvolatile semiconductor memory elements via the transfer gate. Then, the signal may be transferred to the flip-flop circuit and the signal transferred by the flip-flop circuit may be held.
In this case, an SRAM is provided that holds a signal by a flip-flop circuit. For example, when the circuit power supply rises, the output signals from the first and second nonvolatile semiconductor memory elements are transferred to the flip-flop circuit. The signal transferred by the flip-flop circuit is held.
Thereby, the nonvolatile semiconductor memory element of the present invention can be easily incorporated in the SRAM. For this reason, the SRAM can be used as a nonvolatile semiconductor memory device.

A tenth aspect of the present invention is a nonvolatile semiconductor memory device comprising a first nonvolatile semiconductor memory element and a second nonvolatile semiconductor memory element, wherein the first and second nonvolatile semiconductor memory elements are The floating gate type nonvolatile semiconductor memory device includes a floating gate disposed on an FET formed on a semiconductor substrate, a control gate for applying a gate voltage to the floating gate, and a source and a drain. The nonvolatile semiconductor memory device applies a first low voltage to the control gate and a first high voltage to the source when the electric charge is accumulated in the floating gate, and a band-to-band (Band to Band) ) Is generated in the semiconductor substrate to inject and accumulate charges in the floating gate, and a second low voltage is applied to the control gate when erasing the charges accumulated in the floating gate. A second high voltage is applied to the source, a hot hole due to band-to-band is generated in the semiconductor substrate, and the charge accumulated in the floating gate is erased by the hot hole. (Second low voltage <first low voltage <second high voltage <first High voltage). Further, the source of the first nonvolatile semiconductor memory element is connected to the first source line SL, the source of the second nonvolatile semiconductor memory element is connected to the second source line SR, and the first nonvolatile semiconductor memory element is connected. The drain of the conductive semiconductor memory element and the first transfer gate are connected, and the drain of the second nonvolatile semiconductor memory element and the second transfer gate are connected, and the first and second nonvolatile semiconductor memories are connected. When reading data from the element, a predetermined gate voltage is applied to each of the control gate of the first nonvolatile semiconductor memory element and the control gate of the second nonvolatile semiconductor memory element, and the first The output signal from the drain of the second nonvolatile semiconductor memory element is read by turning on the transfer gate.
In this case, two non-volatile semiconductor memory elements are provided as memory cells, and this memory cell applies a voltage between the control gate and the source during the charge accumulation in the floating gate, and the band-to-band. The hot electrons are generated and injected into the floating gate and accumulated. Further, when erasing charges, a voltage is applied between the control gate and the source to generate hot holes between bands, and the charges accumulated in the floating gate are erased by the hot holes. The sources of the two memory cells are connected to independent source lines, and the drains are connected to the respective transfer gates. When reading data from the memory cell, a predetermined gate voltage is applied to the control gate of each memory cell, and the transfer gate is turned on to read data from the memory cell.
As a result, a memory is configured using two nonvolatile semiconductor memory elements (memory cells) of the present invention, and a positive logic signal of data held in the memory and an inverted logic signal of the data can be output independently. In this case, since the source lines of the two memory cells are independent, at the time of writing data to each memory cell array (injecting charge into the floating gate) and erasing (erasing the charge from the floating gate), Different source voltages can be applied to the memory cells.

The nonvolatile semiconductor memory device includes an SRAM (Static Random Access Memory) that holds a signal by a flip-flop circuit, and outputs an output signal from the first and second nonvolatile semiconductor memory elements via the transfer gate. Then, the signal may be transferred to the flip-flop circuit and the signal transferred by the flip-flop circuit may be held.
In this case, an SRAM is provided that holds a signal by a flip-flop circuit. For example, when the circuit power supply rises, the output signals from the first and second nonvolatile semiconductor memory elements are transferred to the flip-flop circuit. The signal transferred by the flip-flop circuit is held.
Thereby, the nonvolatile semiconductor memory element of the present invention can be easily incorporated in the SRAM. For this reason, the SRAM can be used as a nonvolatile semiconductor memory device.

A power supply line to the flip-flop circuit in the SRAM is connected to a power source via a power switch transistor, and controls the on / off of the power switch transistor to apply power to the flip-flop circuit. Also good.
In this case, power is supplied to the flip-flop circuit in the SRAM through the power switch transistor. As a result, the data held in the storage unit can be transferred to the SRAM at a desired timing.

According to an eleventh aspect of the present invention, a plurality of storage units including a first nonvolatile semiconductor memory element and a second nonvolatile semiconductor memory element are arranged, and the first and second storage units in the selected storage unit are arranged. A nonvolatile semiconductor memory device including a sense amplifier for inputting an output signal from a nonvolatile semiconductor memory element and amplifying the input signal, wherein the first and second nonvolatile semiconductor memory elements are formed on a semiconductor substrate. The floating gate type nonvolatile semiconductor memory device includes a floating gate disposed on the FET, a control gate for applying a gate voltage to the floating gate, and a source and a drain. The nonvolatile semiconductor memory device applies a first low voltage to the control gate and a first high voltage to the source when the electric charge is accumulated in the floating gate, and a band-to-band (Band to Band) ) Is generated in the semiconductor substrate to inject and accumulate charges in the floating gate, and a second low voltage is applied to the control gate when erasing the charges accumulated in the floating gate. A second high voltage is applied to the source, a hot hole due to band-to-band is generated in the semiconductor substrate, and the charge accumulated in the floating gate is erased by the hot hole. (Second low voltage <first low voltage <second high voltage <first High voltage). The first nonvolatile semiconductor memory element, the drain, and the first transfer gate are connected in each storage unit, and the drain and the second transfer gate of the second nonvolatile semiconductor memory element are connected. The sources of the first nonvolatile semiconductor memory elements in each storage unit are commonly connected to the first source line S, and the sources of the second nonvolatile semiconductor memory elements are commonly connected to the second source line SB. The The sense amplifier includes a latch circuit in which the gates of the pair of transistors are connected to the drain of the other transistor, and the output of the first transfer gate in each storage section is one of the latch circuits of the sense amplifier. And the output of the second transfer gate is commonly connected to the gate of the other transistor of the latch circuit of the sense amplifier, and the first nonvolatile semiconductor memory element in each storage unit Are connected to the first control gate line CGn, and the gate of the second nonvolatile semiconductor memory element is connected to the second control gate line CGnB. When selecting a desired storage unit from the plurality of storage units, the transfer gate in the desired storage unit is turned on, and the first and second control gate lines CGn corresponding to the storage unit are turned on. By activating CGnB, output signals from the first and second nonvolatile semiconductor memory elements are transferred to the latch circuit in the sense amplifier via the transfer gate.
In this case, a plurality of storage units including two nonvolatile semiconductor memory elements as memory cells are arranged. In this memory cell, when charge is accumulated in the floating gate, a voltage is applied between the control gate and the source to generate hot electrons by band-to-band, and the hot electrons are injected into the floating gate. Accumulate. Further, when erasing charges, a voltage is applied between the control gate and the source to generate hot holes between bands, and the charges accumulated in the floating gate are erased by the hot holes. In each memory portion, a transfer gate is connected to each of the drains of the two memory cells, and the sources of the two memory cells in each memory portion are commonly connected to independent source lines. When a desired storage unit is selected from a plurality of storage units, a memory cell is activated by turning on a transfer gate in the desired storage unit and activating a control gate line corresponding to the storage unit. The output signal from is transferred to the latch circuit in the sense amplifier.
Thus, a nonvolatile semiconductor memory device in which a plurality of storage units using the nonvolatile semiconductor memory element of the present invention are arranged can be configured.

A twelfth aspect of the present invention is a nonvolatile semiconductor memory device comprising a first nonvolatile semiconductor memory element and a second nonvolatile semiconductor memory element, wherein the first nonvolatile semiconductor memory element and the second nonvolatile semiconductor memory element A non-volatile semiconductor memory device includes a floating gate disposed on an FET formed on a semiconductor substrate, a control gate for applying a gate voltage to the floating gate, and a source and a drain. Consists of. The nonvolatile semiconductor memory device applies a first low voltage to the control gate and a first high voltage to the source when the electric charge is accumulated in the floating gate, and a band-to-band (Band to Band) ) Is generated in the semiconductor substrate to inject and accumulate charges in the floating gate, and a second low voltage is applied to the control gate when erasing the charges accumulated in the floating gate. A second high voltage is applied to the source, a hot hole due to band-to-band is generated in the semiconductor substrate, and the charge accumulated in the floating gate is erased by the hot hole. (Second low voltage <first low voltage <second high voltage <first High voltage). The source of the first nonvolatile semiconductor memory element is connected to the first source line S, the source of the second nonvolatile semiconductor memory element is connected to the second source line SB, and the first nonvolatile semiconductor memory element is connected to the first nonvolatile semiconductor memory element. The gate of the conductive semiconductor memory element is connected to the first word line WLn, the gate of the second nonvolatile semiconductor memory element is connected to the second word line WLnB, and the drain of the first nonvolatile semiconductor memory element Is connected to the first data line D, and the drain of the second nonvolatile semiconductor memory element is connected to the second data line DB.
In this case, two non-volatile semiconductor memory elements are provided as memory cells, and this memory cell applies a voltage between the control gate and the source during the charge accumulation in the floating gate, and the band-to-band. The hot electrons are generated and injected into the floating gate and accumulated. Further, when erasing charges, a voltage is applied between the control gate and the source to generate hot holes between bands, and the charges accumulated in the floating gate are erased by the hot holes. The sources of the two memory cells are connected to independent source lines, and the drains are connected to independent data lines. When reading data from the memory cell, a predetermined gate voltage is applied to the control gate of each memory cell.
Thus, a memory is configured using two nonvolatile semiconductor memory elements of the present invention, and a positive logic signal of data held in the memory and an inverted logic signal of the data can be output independently.

According to a thirteenth aspect of the present invention, a plurality of storage units including a first nonvolatile semiconductor memory element and a second nonvolatile semiconductor memory element are arranged, and the first and second nonvolatiles in the selected storage unit are arranged. The nonvolatile semiconductor memory device includes a sense amplifier that inputs an output signal from the conductive semiconductor memory element through a transfer gate unit driven by a column selection signal and amplifies the input signal. The first and second nonvolatile semiconductor memory elements include a floating gate disposed on an FET formed on a semiconductor substrate, a control gate for applying a gate voltage to the floating gate, a source and a drain. And a first low voltage is applied to the control gate and a first high voltage is applied to the source during charge accumulation in the floating gate. (Band to Band) hot electrons are generated in the semiconductor substrate, and charges are injected and accumulated in the floating gate. At the time of erasing the charges accumulated in the floating gate, a second low voltage is applied to the control gate. And applying a second high voltage to the source In addition, a hot hole due to band-to-band (Band to Band) is generated in the semiconductor substrate, and the charge accumulated in the floating gate is erased by the hot hole (second low voltage) <First low voltage <second high voltage <first high voltage). Further, the source of the first nonvolatile semiconductor memory element in each storage unit is commonly connected to the first source line S, and the source of the second nonvolatile semiconductor memory element is commonly connected to the second source line SB. Further, the drain of the first nonvolatile semiconductor memory element in each storage section is commonly connected to the first transfer gate of the transfer gate section, and the drain of the second nonvolatile semiconductor memory element is the transfer gate. A first transfer gate of each of the storage sections, and a gate of the first nonvolatile semiconductor memory element in each storage section is connected to a first word line WLn for selecting the nonvolatile semiconductor memory element, The gate of the second nonvolatile semiconductor memory element is connected to a second word line WLnB for selecting the nonvolatile semiconductor memory element. When selecting a desired storage unit from the plurality of storage units, the first word line WLn and the second word line WLnB in the selected storage unit are activated, and the first and second word lines are activated. By turning on the transfer gate, the output signals from the first and second nonvolatile semiconductor memory elements of the storage unit are transferred to the sense amplifier.
In this case, a plurality of storage units including two nonvolatile semiconductor memory elements as memory cells are arranged. In this memory cell, when charge is accumulated in the floating gate, a voltage is applied between the control gate and the source to generate hot electrons by band-to-band, and the hot electrons are injected into the floating gate. Accumulate. Further, when erasing charges, a voltage is applied between the control gate and the source to generate hot holes between bands, and the charges accumulated in the floating gate are erased by the hot holes. In each storage unit, the sources of the two memory cells are commonly connected to independent source lines. The drain of the first memory cell in each memory portion is commonly connected to the first transfer gate of the transfer gate portion, and the drain of the second memory cell is commonly connected to the second transfer gate of the transfer gate portion. The When a desired storage unit is selected from a plurality of storage units, the control gate of the memory cell in the desired storage unit is activated and the first and second transfer gates of the transfer gate unit are turned on. The output signal from the memory cell is transferred to the latch circuit in the sense amplifier.
Thereby, a memory cell array can be comprised by the memory | storage part using the non-volatile semiconductor memory element of this invention.

In a conventional EEPROM or the like, at the time of erasing, it is necessary to erase the charge while controlling the threshold value of the nonvolatile semiconductor memory element (memory cell) to be on the positive side, which requires a complicated control circuit. .
On the other hand, in the present invention, since the charges in the floating gate of the memory cell are erased by hot holes, it is only necessary to control the voltage of the control gate, and no complicated control circuit is required.
In another aspect of the present invention, the injection of charge into the floating gate of the memory cell is performed by hot electrons, and the charge is erased by hot holes, so that the drain (or source) voltage and the control gate It is only necessary to control the voltage, and no complicated control circuit is required. Further, the threshold value can be set to the positive side or the negative side by controlling the voltage of the control gate. Further, it can be manufactured by a standard CMOS process using a single-layer polysilicon floating gate.

  In addition, since a complicated control circuit is not required, even when a non-volatile memory such as an EEPROM according to the present invention and standard logic are simultaneously embedded in one chip, the yield reduction is reduced and the product price (cost) is reduced. ).

1 is a plan view of a nonvolatile semiconductor memory element according to a first embodiment of the present invention. 1B is an equivalent circuit diagram of the nonvolatile semiconductor memory element of FIG. 1A. FIG. 1B is a cross-sectional view taken along the line A-A ′ of the nonvolatile semiconductor memory element of FIG. 1A. 1B is a B-B ′ cross-sectional view of the nonvolatile semiconductor memory element of FIG. 1A. FIG. 3 is a table for explaining the operation of the memory cell shown in FIG. 1. 3 is a table for explaining the operation of the memory cell shown in FIG. 1. It is a figure for demonstrating the hot hole by a band-band (Band to Band). It is another figure for demonstrating the hot hole by a band-band (Band to Band). It is a figure which shows the Vg-Id characteristic at the time of initial stage, at the time of writing, and erasing. It is a figure which shows the erasing characteristic by the tunnel current of Fowler-Nordheim. It is a figure which shows the erasing characteristic by a band-to-band (Band to Band) electric current. It is another figure which shows the erasing characteristic by a band-to-band (Band to Band) electric current. It is a figure which shows the equivalent circuit of the coupling type | system | group of a memory cell. It is a figure which shows the relationship between control gate voltage VCG and floating gate voltage VFG. It is a figure which shows the structure of the memory element of a 2 layer polysilicon gate structure. It is a figure which shows the structure of the memory cell array based on the 2nd Embodiment of this invention. It is a figure which shows the structure of the memory cell array based on the 2nd Embodiment of this invention. 11 is a table for explaining the operation of the memory cell array shown in FIG. 10. 11 is a table for explaining the operation of the memory cell array shown in FIG. 10. It is a figure which shows the structure of the non-volatile semiconductor memory device which concerns on the 3rd Embodiment of this invention. 7 is a table for explaining an operation of a nonvolatile semiconductor memory device according to a third embodiment of the present invention. It is a figure which shows the process structure employ | adopted as the non-volatile semiconductor memory element which concerns on the 4th Embodiment of this invention. It is a figure which shows the 1st Example of the non-volatile semiconductor memory device based on the 4th Embodiment of this invention. It is a table | surface for demonstrating operation | movement of the 1st Example of the non-volatile semiconductor memory device based on the 4th Embodiment of this invention. It is a figure which shows the 2nd Example of the non-volatile semiconductor memory device based on the 4th Embodiment of this invention. It is a table | surface for demonstrating operation | movement of the 2nd Example of the non-volatile semiconductor memory device based on the 4th Embodiment of this invention. It is a figure which shows the 3rd Example of the non-volatile semiconductor memory device based on the 4th Embodiment of this invention. It is a table | surface for demonstrating operation | movement of the 3rd Example of the non-volatile semiconductor memory device based on the 4th Embodiment of this invention. It is a figure which shows the 4th Example of the non-volatile semiconductor memory device based on the 4th Embodiment of this invention. It is a table | surface for demonstrating the operation | movement of the 4th Example shown in FIG. It is a figure which shows the 5th Example of the non-volatile semiconductor memory device based on the 4th Embodiment of this invention. It is a table | surface for demonstrating operation | movement of the 5th Example shown in FIG. It is a figure which shows the 6th Example of the non-volatile semiconductor memory device based on the 4th Embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

[First Embodiment]
1A to 1D are diagrams showing a configuration of a nonvolatile semiconductor memory element according to a first embodiment of the present invention, and a diagram showing a configuration of a floating gate type EEPROM.

  FIG. 1A shows a plan view of the EEPROM cell. 1B is an equivalent circuit diagram (a diagram for explaining the operation of the memory cell shown in FIG. 1A), FIG. 1C is a cross-sectional view taken along line AA ′ of FIG. 1A, and FIG. A sectional view along is shown.

  As shown in the equivalent circuit of FIG. 1B, the EEPROM cell includes a transistor (FET) Tr, a drain D, a source S, a control gate CG, a floating gate FG, and a capacitor C (FC) between the control gate CG and the floating gate FG. ).

Structurally, in FIG. 1A, 1 is an n-type well (hereinafter referred to as n-well) formed on a p-type semiconductor substrate Psub, 2 is an n + diffusion region formed on the n-well, and 3 is a floating state. Polysilicon gate as a gate, 4 is an n + -type diffusion layer as a drain of the transistor, 5 is an n + -type diffusion layer as a source, 6 is a gate portion of the transistor, and 7 is a contact connecting the metal wiring layer and the diffusion layer , 8 is a metal wiring connected to the drain, 9 is a metal wiring connected to the source, 10 is a gate portion serving as a capacitor of a floating gate, 11 is a metal wiring serving as a control gate, 12 is a contact connecting the n + diffusion layer and the metal wiring 11, Reference numeral 13 denotes a field oxide film for element isolation.

  Next, the operation of this cell will be described. FIG. 2A and FIG. 2B show the voltage relationship of each terminal of the write operation, the erase operation, and the read operation to the memory cell shown in FIG. 1A in a table.

  Referring to FIG. 2A, at the time of writing, the voltage of control gate CG is set to 7V, the voltage of drain D is set to 5V, and the voltage of source S is set to 0V. In this state, the coupling capacitor C (FC) causes the voltage of the floating gate to be about 4.2 V by setting the coupling ratio described later, and the transistor Tr is turned on.

  At this time, since the voltage of the drain D is 5 V, Tr operates in the saturation region and an excessive voltage is applied, so hot electrons are generated and electrons are injected into the floating gate. This state is referred to as a write state. At this time, for example, if the voltage of the drain D is set to 0 V, no current flows through Tr, so that hot electrons are not generated and electrons are not injected into the floating gate. That is, writing is selectively performed.

  On the other hand, at the time of erasing, the voltage of the control gate CG is 1 to 2 V, the voltage of the drain D is 7 V, and the source S is open.

  FIG. 3A is a diagram showing the generation of hot holes between bands (Band to Band). The voltage Vcg of the control gate CG is 0 V, the voltage Vd of the drain D is high (Vd = high), and the source S is Open. First, electric field concentration of the depletion layer occurs in the vicinity of the drain D.

  Then, as shown in FIG. 3B, a so-called high energy band-to-band current flows, and a hole-electron pair is generated. Some holes (hot holes) having high energy are taken into the floating gate FG. Hereinafter, the band-to-band (Band to Band) is also simply referred to as “B to B”.

When the voltage is further increased and an over electric field is applied to the oxide film between the floating gate and the Fowler-Nordheim tunnel current, electrons flow from the floating gate FG to the drain D. When the voltage is further increased, a junction breakdown occurs and a large current flows through the substrate. This breakdown voltage is assumed to be VBD.

  As described above, when writing or erasing is performed on the floating gate, the number of electrons in the floating gate increases or decreases, and as a result, the threshold value between the control gate and the source changes.

For details on band-to-band (B to B) current, refer to “Reference:“ Flash Memory Technology Handbook ”, Editor: Fujio Takaoka, Publisher: Science Forum, Inc., August 15, 1993, 1st edition, 1st edition issued. See Chapter 5, Section 2, Analysis of Band-to-Band Tunneling in Non-volatile Memory Cells, P206-215.

  FIG. 7 in this document shows the results of measuring the drain current and the drain-gate voltage dependence, and shows how the drain current changes before the avalanche breakdown occurs as the drain voltage is increased. Has been.

FIG. 4 is a diagram showing characteristics (Vg-Id characteristics) of the control gate voltage Vg and the drain current Id at the initial time (Initial), at the time of writing (Program), and at the time of erasing (Erase). As shown in FIG. 4, if this cell is over-erased (over-erased), the threshold value becomes negative, and the limit point is defined as Erase (Limit). In addition, if the threshold value becomes negative due to over-erasing, the characteristics of Erase (
Over).

FIG. 5 shows the erase characteristics of Fowler-Nordheim due to the tunnel current.
Indicates the erase time and threshold. Since the erasing characteristic by the tunnel current depends on the electric field, the erasing characteristic is substantially linear with respect to Log (t) expressing the time t in logarithm. In this case, if the erasing time is too long, overerasing (overerasing) occurs, so that the time control is very difficult.

  FIG. 6A shows the erase characteristics by BtoB. In BtoB, excessive electrons and holes are generated in the vicinity of the drain of the substrate. Therefore, when the floating gate is almost neutral, the erasing characteristic is saturated. In the experiment, it is slightly saturated on the negative side. However, if the threshold value is somewhat negative, this cell will cause a leak, which is a problem. In order to solve this problem, at the time of erasing, a bias (VCG = 1v) is applied to the control gate to control erasing. Thus, by applying a bias voltage to the control gate, the threshold value can be maintained on the positive side even in the case of overerasing (overerase).

FIG. 7 shows an equivalent circuit of the coupling system of this memory cell.
If the state of the floating gate is the initial state (neutral state), the total charge of this system is zero, so (VCG−VFG) * C (FC) + (Vsub−VFG) * C (FB) + (VD -VFG) * C (FD) + (VS-VFG) * C (FS) = 0. When C (FC) + C (FB) + C (FD) + C (FS) = CT (total), VFG = VCG * C (FC) / CT + Vsub * C (FB) / CT + VD * C (FD) / CT + VS * C (FS) / CT where C (FD) = C (FS) ≈0 and Vsub = VS = 0, VFG = VCG * C (FG) / {C (FC) + C (FB)} where If C (FG) / {C (FC) + C (FB)} = α (coupling ratio), VFG = αVCG. Usually, α≈0.6 is set.

  For example, if VCG = 1v in the neutral state, the voltage VFG of the floating gate is 0.6v, and the hole is equivalently injected. Therefore, if BtoB is erased in this state, it is shifted upward by 1v as shown in the graph of FIG. 6, and can be converged to the threshold of the erase limit point. Thus, by setting the voltage of VCG at the time of erasing to an optimum positive voltage, it is possible to set an arbitrary threshold value and prevent over-erasing.

  The operation of this memory cell is shown in FIG. 2A. In writing, when CG is 7v, drain D is 5v, and source S is 0v, hot electrons are generated and electrons are injected into the floating gate FG.

  In erasing, 1 to 2 v is applied to the CG in order to set a threshold value after erasing. When the drain D is 7v and the source S is open, BtoB hot holes are generated, holes are injected into the floating gate (electrons are emitted), and erased.

  For reading, CG is 3v, the drain is 1v, and the source S is 0v. It is turned off (“0”) if the threshold value is 3 v or more after writing, and turned on (“1”) if it is erased and the threshold value is 0.5 v.

  FIG. 8 shows the relationship between the voltage VCG applied to the control gate and the voltage VFG applied to the floating gate. As shown in the figure, when the control gate voltage VCG is increased, the floating gate voltage VFG is increased in proportion thereto.

  As described above, the first embodiment of the present invention has been described by taking the single-layer polysilicon gate memory element shown in FIG. 1 as an example in which a standard CMOS process is used. Even when a memory element having a two-layer polysilicon gate structure capable of reducing the area is used, the operation is the same.

  FIG. 9 is a diagram showing a configuration of a memory element having a two-layer polysilicon gate structure. As shown in FIG. 9, a two-layer polysilicon gate structure in which the control gate CG and the floating gate FG are each composed of polysilicon can be formed.

[Second Embodiment]
The example of the nonvolatile semiconductor memory element (memory cell) has been described above as the first embodiment of the present invention. Next, as the second embodiment of the present invention, this memory cell is incorporated into a matrix array. An embodiment of the nonvolatile semiconductor memory device in this case will be described.

FIG. 10 is a diagram showing a configuration of a nonvolatile semiconductor memory device according to the second embodiment of the present invention.
As shown in FIG. 10, memory cells M11 to Mmn are arranged on a matrix to form a memory cell array. These memory cells M11 to Mmn are floating gate type nonvolatile semiconductor memory elements according to the present invention.

  In FIG. 10, word lines WL1 to WLm are selected by a row decoder (not shown), and data lines D1 to Dn are selected by a column decoder (not shown).

  The control gate CG of the memory cells M11, M12 to M1n is connected to the word line WL1. A control gate CG of the memory cells M21, M22 to M2n is connected to the word line WL2. Similarly, control gates CG of memory cells Mm1, Mm2,... Mmn are connected to word line WLm.

  The data line D1 is connected to the drains D of the memory cells M11, M21 to Mm1. The data line D2 is connected to the drains D of the memory cells M12, M22, to Mm2. Similarly, drains D of memory cells M1n and M2n to Mmn are connected to the data line Dn.

The sources S of the memory cells M11 and M21 to Mmn are connected to a commonly connected source line Source. The commonly connected source line Source is connected to the source control circuit 200. In the source control circuit 200, an Nch (N-type channel) transistor 201 driven by an R / W signal at the time of reading and writing and a Pch (P-type channel) transistor 202 driven by an Erase signal at the time of erasing are connected in series. Connected to and configured.
A connection point between the transistor 201 and the transistor 202 is connected to the source line Source. In the source control circuit 200, the source line Source is set to 0v by the transistor 201 at the time of reading and writing. Further, the source line Source is biased to a desired bias voltage Vb by the transistor 202 at the time of erasing.

  FIG. 11A is a diagram for explaining the operation of the memory cell array shown in FIG. The table shown in FIG. 11B shows an example of a memory that performs erasing on the drain side, and the table shown in FIG. 11C shows an example of a memory that performs erasing on the source side.

  As shown in the table of FIG. 11B, when erasing the accumulated charge on the drain side, only the accumulated charge of the memory cell connected to the selected word line and the batch erase mode in which the accumulated charge of all the memory cells is erased simultaneously. The page erase mode for erasing and the bit erase mode for erasing the accumulated charge of only one selected memory cell can be selected.

  As shown in the table of FIG. 11C, when erasing accumulated charges on the source side, a batch erase mode in which accumulated charges of all memory cells are simultaneously erased and accumulation of memory cells connected to a selected word line are performed. A page erase mode in which only charges are erased can be selected.

First, the case where charge is erased on the drain side will be described with reference to the table shown in FIG. 11B.
In the collective erase mode, 1 v is applied to the word lines WL1 and WL2 to m as a bias voltage for giving a positive threshold when erasing charges in the memory cell. 7 v is applied to the data lines D1, D2 to n as a bias voltage necessary for generating hot holes. For example, 2 v is applied as an appropriate bias voltage for opening the commonly connected source line Source or turning off the memory cell. In this state, all memory cells are erased simultaneously.

  Next, in the page erase mode, 1 v is applied to the word line WL1 as a bias voltage for giving a positive threshold value when erasing charges in the memory cell. Further, 4 v is applied to the other word lines WL2 to m as a bias voltage for relaxing the electric field and suppressing the generation of hot holes. 7 v is applied to the data lines D1 to Dn as a bias voltage necessary for generating hot holes. The commonly connected source line Source is opened, or 4 v is applied as a bias voltage for turning off the memory cell.

  In this state, the memory cells M11 to M1n connected to the word line WL1 are erased. However, since the memory cells connected to the word lines WL2 to WLm have a high gate voltage of 4v, the electric field with the drain becomes weak and BtoB Hot holes are less likely to occur and are not erased. Therefore, only the memory cells M11 to M1n connected to the word line WL1 are erased.

  In the bit erase mode, for example, when performing bit erase of the memory cell M11, 1v is applied to the word line WL1, 4v is applied to the word lines WL2 to m, 7v is applied to the data line D1, and an open or bias 4v is applied to the data lines D2 to Dn. To do. Further, the source line Source is opened or 4v is applied. In this state, only the memory cell M11 is erased.

  Writing and reading are performed by applying a voltage to the word line WL1 and the data line D1 when the selected memory cell, for example, M11 is selected.

Next, the case where charge is erased on the source side will be described with reference to the table shown in FIG. 11C.
In the batch erase mode, 1 v is applied to the data lines WL1 to WLm as a bias voltage for giving a positive threshold when erasing charges in the memory cells. 2 v is applied as a bias voltage for opening the data lines D1 to Dn or turning off the memory cells. Further, 7 v is applied to the commonly connected source line Source as a bias voltage necessary for generating hot holes. As a result, the accumulated charges are erased in all the memory cells.

  In the page erase mode, 1v is applied to the word line WL1 as a bias voltage for giving a positive threshold when erasing charges in the memory cell, and the bias voltage 4v is applied to the other word lines WL2 to m. When applied, the electric field of the unselected memory cells is relaxed and not erased, and only the WL1 cell is erased. Writing and reading are the same operation.

As an advantage of erasing on the source side, since damage at the hot hole occurs on the source side, the drain side at the time of reading is not affected, and a good result can be expected in reliability.
Another advantage is that since a high voltage is applied only to the source side, a drain side circuit (such as a column decoder (not shown)) can be composed of low voltage transistors, improving circuit characteristics and reducing layout area. Can be expected.

  The first bias voltage described above corresponds to the bias voltage “1v” for providing a positive threshold when erasing charges in the memory cell. The aforementioned second bias voltage corresponds to the bias voltage “4v” for relaxing the electric field and suppressing the generation of hot holes.

  The bias voltage A described above corresponds to a bias voltage “1v” for giving a positive threshold when erasing charges in the memory cell. The aforementioned bias voltage B corresponds to the bias voltage “7v” necessary for generating hot holes. The aforementioned bias voltage C corresponds to a bias voltage “2v” for turning off the memory cell. The bias voltage D described above corresponds to a bias voltage for relaxing the electric field and preventing the generation of hot holes, or a bias voltage “4v” for turning off the memory cell.

[Third Embodiment]
FIG. 12A is a diagram showing a configuration of a nonvolatile semiconductor memory device according to the third embodiment of the present invention. FIG. 12A shows an example of a memory cell array in which source lines are provided in parallel with drain lines. The memory cell array shown in FIG. 12A differs from the memory cell array shown in FIG. 10 in that the source lines S1 to Sn1 are provided independently in parallel with the drain lines D1 to Dn, and the other configurations are the same. is there.

  In the memory cell array shown in FIG. 12A, the source S of the memory cells M11 to Mm1 is connected to the source line S1. The source S of the memory cells M12 to Mm2 is connected to the source line S2. Similarly, the source S of the memory cells M1n to Mmn is connected to the source line Sn.

  FIG. 12B is a table showing the operation modes of the memory cell array shown in FIG. 12A.

  As shown in FIG. 12B, even when the stored charge is erased on the source side, only the stored charge of the memory cell connected to the selected word line and the batch erase mode in which the stored charge of all the memory cells is erased simultaneously. The page erase mode for erasing and the bit erase mode for erasing the accumulated charge of only one selected memory cell can be selected.

  In the table of FIG. 12B, in the batch erase mode, 1 v is applied to WL1, WL2 to m, D1, D2 to n are open, and 7 V is applied to S1 and S2 to n. In this state, all memory cells are erased simultaneously. That is, all memory cells are erased from the source side.

  Next, in the page erase mode, 1v is applied to WL1, and 4v is applied to WL2 to m. D1 to Dn are set to open, and 7V is applied to S1 and S2 to n. In this state, M11 to M1n connected to WL1 are erased, but the memory cells connected to WL2 to WLm have a high gate voltage of 4v, so the electric field with the source becomes weak and BtoB hot holes are generated. It becomes difficult and will not be erased. Therefore, only WL1 is erased.

  In the bit erase mode, for example, when performing bit erase of the memory cell M11, 1v is set to WL1, 4v is set to WL2 to m, D1, D2 to Dn are open, 7v is set to S1, and S2 to n are open. In this state, only M11 is erased.

  For writing and reading, when a selected memory cell, for example, M11 is selected, writing or reading is performed by applying a voltage to WL1 and D1.

  As described above, the nonvolatile semiconductor memory element and the nonvolatile semiconductor memory device of the present invention have been described. In the above-described embodiment, the writing by hot electrons has been described as an example of writing. Writing with a Fowler-Nordheim tunnel current is also possible by applying a high voltage of about 15V. However, writing with a tunnel current requires a relatively high voltage.

  As described above, in a conventional EEPROM or the like, it is necessary to erase charges while controlling the threshold value to be on the positive side at the time of erasing, and thus a complicated control circuit is required. On the other hand, in the present invention, since the charges in the floating gate are erased by hot holes, it is only necessary to control the voltage of the control gate, and no complicated control circuit is required.

[Fourth Embodiment]
Next, as a nonvolatile semiconductor memory element according to the fourth embodiment of the present invention, a case where the potential of the control gate at the time of erasing becomes negative in the nonvolatile semiconductor memory element according to the first embodiment will be described. To do. The description overlapping with the nonvolatile semiconductor memory element according to the first embodiment is omitted.

  Referring to FIG. 2B, in writing, when the control gate CG is 3v, the drain D is 9v, and the source S is open, a hot hole (Hot Hole) by band-to-band in the vicinity of the drain. Since hot electrons are generated and the gate voltage is positive, hot electrons are injected into the floating gate and accumulated as electric charges.

  At this time, when the drain D is set to 7v, the gate voltage is increased to 3v, so that hot holes and hot electrons are not generated and writing does not occur. This condition is write-protected.

  In the erasing, when the control gate CG is set to −1 v to 0 v, the drain D is set to 7 v, and the source S is opened, a hot hole (Hot Hole) is generated in the vicinity of the drain due to band-to-band. Holes are injected and the accumulated charge is erased. When a negative bias is applied to the control gate CG, the potential of the floating gate becomes negative, so that erasure is more likely to occur.

  In a MOSFET, the source and drain structures are symmetric, so that the same write and erase operations can be performed even if the drain is open and a voltage is applied to the source side.

  Further, in reading, when the control gate CG is set to 0 to 3 v, the drain D is set to 1 v, and the source S is set to 0 v, when the write is performed and the threshold value is 3 v or more, no current flows and “0” is determined. If the threshold value is negative or less than 3v after erasing is performed, a current flows and it is determined as “1”.

  As described above, when writing or erasing is performed on the floating gate, the number of electrons in the floating gate increases or decreases, and as a result, the threshold value between the control gate and the source changes.

  The first low voltage corresponds to the voltage “3v” applied to the control gate of FIG. 2B, and the second low voltage corresponds to the voltage “−1 to 0 v” applied to the control gate of FIG. 2B. . The first high voltage corresponds to the voltage “9v” applied to the control gate of FIG. 2B, and the second high voltage corresponds to the voltage “7v” applied to the drain of FIG. 2B.

  Further, in FIG. 6B showing the erase characteristics by BtoB, the threshold value can be controlled by changing the voltage VCG of the control gate. In the case of “VCG = 0v” shown in the graph of (a) in the figure, the threshold value can be made slightly negative. In the case of “VCG = 1v” shown in the graph of (b) in the figure, the threshold value can be positive (for example, 1V), and “VCG = −1v” shown in the graph of (c) in the figure. In this case, the threshold value can be negative (for example, -1 V). Thus, the threshold value can be changed by controlling the voltage of the control gate. In the present invention, this characteristic is utilized.

  For example, if the control gate voltage VCG is 1 v (VCG = 1 v) in the neutral state, the floating gate voltage VFG is 0.6 V (VFG = 0.6 v), and a hole is equivalently injected. Accordingly, when BtoB is erased in this state, the shape is shifted upward by 1v as shown in the graph of FIG. 6B, and can be converged to a positive threshold value. Conversely, when the control gate voltage VCG is set to −1v, the graph is shifted downward as shown in FIG. 6B (c), and electrons are injected. Thus, by setting the control gate voltage VCG to an optimum voltage at the time of erasing, it is possible to set an arbitrary threshold value and to prevent over-erasing.

  The operation of this memory cell is the same as in FIG. 2B, and a duplicate description is omitted.

Here, a method of applying a negative voltage to the control gate CG will be described.
FIG. 13 is a diagram showing a process structure employed in the nonvolatile semiconductor memory device of the present invention. As shown in FIG. 13, on a P-type substrate (Psub), a well structure (non-right side of the drawing) that constitutes a non-volatile element and a well structure (on the left side of the drawing) that constitutes a high-voltage transistor constituting a control circuit. ).

The fine transistor of the non-volatile element includes, for example, a non-volatile NMOS element NV-NMOS (Non-Volatile-N channel M) in a Deep-Nwell (DNW) formed on the Psub.
A P-well (PW) for producing etal-Oxide-Semiconductor and an N-well (NW) for producing a nonvolatile PMOS element NV-PMOS are configured.

  The well voltage VPW is applied to the NMOS P-well, and the well voltage VNW is applied to the PMOS N-well. Further, terminals D and S for applying a measurement voltage are connected to the drain and source of the nonvolatile element, respectively.

  On the other hand, for the purpose of supplying a high voltage to the non-volatile element, a 20v (volt) type transistor has a P-well for high voltage (HPW) for making a 20v type NMOS on Psub as shown on the left side of the figure. , A high voltage N-well (HNW) for forming a 20v PMOS is constructed.

  The source of the NMOS transistor, Psub, is commonly connected to Vss. The source of the PMOS transistor, well (HNW) is connected to Vpp. When this structure is adopted, the NV-MOS well and the 20v well can be electrically separated, and thus different voltages can be applied to the well.

  Here, Vss = −2v to 0v and Vpp = 3v to 9v. This structure itself is often used for products such as a flash memory in which a positive voltage is applied to the P-well of a memory cell during erasing.

  As described above, as an embodiment of the present invention, the case where the standard CMOS process is used has been described by taking the one-layer polysilicon gate memory element shown in FIG. 1A as an example. The operation is the same even when a memory element having a two-layer polysilicon gate structure which can be reduced is used.

  Next, as an application example of the nonvolatile semiconductor memory element (memory cell) of the present invention, an example of a nonvolatile semiconductor memory device including a memory cell array configured by using the nonvolatile semiconductor memory element of the present invention as a memory cell will be described.

  FIG. 14A is a diagram showing a first example of a nonvolatile semiconductor memory device of the present invention. The nonvolatile semiconductor memory device shown in FIG. 14A includes an SRAM 100 and a storage unit 200 using the nonvolatile semiconductor memory element of the present invention.

  The SRAM 100 is an SRAM that holds data, and shows a circuit configuration of a well-known single port SRAM (SP-SRAM). The SRAM 100 includes switching transistors 101 and 102, transistors 111 and 112 constituting a left inverter, and transistors 121 and 122 constituting a right inverter. The input and output of the two inverters are connected to each other to form a flip-flop.

  The transistors 201 and 202 of the storage unit 200 are transistors serving as transfer gates for transferring data, and the transistors (memory cells) 202 and 204 are floating gate type nonvolatile semiconductor memory elements (memory cells) of the present invention.

  The gates of the inverter transistors 111 and 112 in the SRAM 100 are connected to the transfer gate transistor 201 in the storage unit 200. The gates of the inverter transistors 121 and 122 in the SRAM 100 are connected to the transfer gate transistor 203 in the storage unit 200.

  The first nonvolatile semiconductor memory element described above corresponds to the transistor (memory cell) 202, and the second nonvolatile semiconductor memory element corresponds to the transistor (memory cell) 204. In addition, the first transfer gate corresponds to the transistor 201, and the second transfer gate corresponds to the transistor 203.

The operation of this memory is shown in FIG. 14B. Although not shown, as an initial setting of the memory cell, a state in which electrons are injected is set. In order to inject electrons into this memory cell, the gate signal TRF of the transistors 201 and 203 serving as transfer gates is 0 v, the gate signals CGL and CGR are 3 v, and the source is 9 V. In this state, electrons are injected into the floating gates of the transistors (memory cells) 202 and 204.
Referring to FIG. 14B, the writing is performed by setting the gate signal TRF of the transistors 201 and 203 serving as transfer gates to 0 v, the gate signal CGL (left cell) to 3 v, the gate signal CGR (right cell) to 0 to -2 v, and the source S. 7v is applied. The left memory cell 202 has a reduced electric field and is not erased, and the right memory cell 204 is erased. This state is defined as writing.

  On the other hand, in erasing, if the gate signal TRF is 0v, the control gate CGL is 0 to -2v, the control gate CGR is 3v, and the source S is 7v, the left cell 202 is erased and the right cell 204 is not erased. This state is assumed to be erased.

  In the cell data transfer mode, the data in the storage unit 200 is transferred to the SRAM 100. The transfer is basically performed when the power is turned on. The gate signal TRF of the transfer gate is set to Vcc applied state, and CGL, CGR, and S are set to 0v. Here, when data is written in the storage unit 200, the right memory cell 204 is erased. Therefore, when the power supply Vcc gradually rises, the memory cell 202 is turned off and the memory cell 204 is turned on. Since the signal Bit becomes a voltage lower than the signal BitB, the setting of the SRAM 100 results in that Bit is set to 0v and BitB is set to Vcc.

  On the other hand, when the storage unit 200 is in the erased state, when the power is turned on, the memory cell 202 is on and the memory cell 204 is off, so that Bit is set to Vcc and BitB is set to 0v.

  In the SRAM reading, the gate signal TRF of the transfer gate is 0 v, the word line WL is 3 v (Vcc), and the signals CGL, CGR, and the source S are 0 v. Since the TRF is 0v, the memory cells 202 and 204 are disconnected from the SRAM, so that after the power is turned on, the memory operates in the same manner as the SRAM.

What is characteristic here is that a voltage of up to 9v is applied to the memory cells 202 and 204, so it is recommended to use a medium voltage MOS, for example, a 3v MOS transistor, but the SRAM 100 and the switch transistors 201 and 202 are used. Since a high voltage is not applied, a low voltage MOS transistor, for example, a 1v type MOS can be used. Therefore, it is suitable for miniaturization and a memory having a small area can be realized.

  FIG. 15A shows a second embodiment of the nonvolatile semiconductor memory device of the present invention. The nonvolatile semiconductor memory device shown in FIG. 15A is structurally different from the nonvolatile semiconductor memory device shown in FIG. 14A in that the source S in FIG. 14A is the source SL for the left memory cell 202 and the right memory cell. The other points are the same as those of the nonvolatile semiconductor memory device shown in FIG. 14A. For this reason, the same code | symbol is attached | subjected to the same component and the overlapping description is abbreviate | omitted. With such a configuration, the voltage applied to the source can be set independently, and rewriting becomes easy.

  The first source line SL described above corresponds to the source line SL, and the second source line SR corresponds to the source line SR.

  The operation of this memory is shown in FIG. 15B.

  Referring to FIG. 15B, writing is performed by setting the gate signal TRF for the transfer gate to 0 v, the word line WL to 0 v, the gate signal CGL to 3 v, CGR to −2 v, the source SL to 9 v, and the source SR to 7 v. Electrons are injected into the left memory cell 202 to raise the threshold value, and the right memory cell 204 is erased to emit electrons to lower the threshold value.

  On the contrary, when the gate signal TRF for the transfer gate is set to 0 v, the word line WL is set to 0 v, the gate signal CGL is set to −2 v, the CGR is set to 3 v, the source SL is set to 7 v, and the SR is set to 9 v, the threshold value of the memory cell 202 is The threshold value of the memory cell 204 is increased. Since the state of the write / erase cell is reversible, repeated write / erase can be easily realized. The cell data transfer and SRAM read modes are the same as in the embodiment of FIG.

  FIG. 16A shows a third embodiment of the nonvolatile semiconductor memory device of the present invention. The configuration of the nonvolatile semiconductor memory device shown in FIG. 16A is different from that of the nonvolatile semiconductor memory device shown in FIG. 15A in that a switching transistor 131 is provided on the power supply side of the SRAM 100 in FIG. Is the same as the nonvolatile semiconductor memory device shown in FIG. 15A. For this reason, the same code | symbol is attached | subjected to the same component. A SET signal is connected to the gate 131.

The operation of this memory is illustrated by FIG. 16B.
The difference between FIG. 16B and FIG. 15B is the state of cell data transfer. In the example of FIG. 16B, the power supply Vcc has already been started during cell data transfer. At this time, when the gate signal TRF is set to Vcc and the gate signal SET is gradually switched from Vcc to 0 v, the state is the same as when the power is turned on, and the flip-flop of the SRAM 100 is set corresponding to the state of the cell. Is done.

  FIG. 17 shows a fourth embodiment of the nonvolatile semiconductor memory device of the present invention. FIG. 17 shows an embodiment in which the storage unit 500 is composed of m memory arrays.

  In FIG. 17, reference numeral 300 denotes a main amplifier that amplifies and outputs data, and 400 denotes a first-stage amplifier that amplifies cell data. The sense amplifier 400 includes transistors 401 and 404 for a latch circuit having gates crossed with transistors 401 and 402 serving as current sources as loads, and a transistor 405 for activating the sense amplifier 400.

  A sense enable signal SEN for turning on the transistor 405 and activating the sense amplifier 400 is input to the gate of the transistor 405. The drains of the transistors 403 and 404 are connected to a main amplifier (Main Amp) 300 via signal lines SO and SOB.

  Further, the gates of the transistors 403 and 404 are connected to the transfer gates in the memory portions 500-1 to 500-m by signal lines D and DB.

  The storage units 500-1 to 500-m are composed of transistors 501 and 503 serving as transfer gates and memory cells 502 and 504 which are nonvolatile semiconductor memory elements according to the present invention.

  A signal SEL1 that is selected when cell data is transferred to the sense amplifier 400 is connected to the gates of the transfer gate transistors 501 and 503 of the storage unit 500-1. Gate signals CG1 and CG1B are connected to the gates of the memory cells 502 and 504, respectively. The source of the memory cell 502 is connected to the signal line S, and the source of the memory cell 504 is connected to the signal line SB.

  Similarly, signal lines SEL2, CG2, and CG2B are connected to the storage unit 500-2, and sources are connected to the signal lines S and SB, respectively. Similarly, signal lines SELm, CGm, and CGmB are connected to the storage unit 500-m, and sources are connected to the signal lines S and SB, respectively.

  The aforementioned sense amplifier corresponds to the sense amplifier 400, the aforementioned first nonvolatile semiconductor memory element corresponds to the transistor (memory cell) 502, and the second nonvolatile semiconductor memory element corresponds to the transistor (memory cell) 504. Corresponds. Further, the above-described first transfer gate corresponds to the transistor 501 and the second transfer gate corresponds to the transistor 503. The first source line described above corresponds to the source line S, and the second source line SB corresponds to the source line SB. The first control gate line CGn corresponds to the control gate lines CG1 to CGm, and the second control gate line CGnB corresponds to the control gate lines CG1B to CGmB.

  The operation of this memory array is shown in FIG. Note that FIG. 18 illustrates the operation of the memory cell of the memory portion 500-1 as an example.

  Referring to FIG. 18, the write gate signal SEL1 of the transfer gate is set to 0v, the control gate signal CG1 is set to 2v, the control gate signal CG1B is set to -2v, the source S is set to 9v, and the source SB is set to 7v.

  In this writing state, the nonvolatile semiconductor memory element (memory cell) 502 is turned off because electrons are injected into the floating gate and the threshold value is increased. Further, since holes are injected into the memory cell 504, the threshold value is lowered and the memory cell 504 is turned on. At this time, since the gate signal SEL1 of the transfer gate is 0v and the transistors 501 and 503 are off, the levels of the signal lines D and DB are not fixed and the sense amplifier 400 does not need to be activated yet. The signal SEN is 0v. Of course, the outputs SO and SOB of the sense amplifier are not fixed.

  For erasing, when the gate signal SEL1 of the transfer gate is set to 0v, the gate signal CG1 is set to -2v, the gate signal CG1B is set to 2v, the source S is set to 7v, and the source SB is set to 9v, the memory cell 502 injects holes into the floating gate. Therefore, the threshold value is lowered and the on state is entered. In addition, the nonvolatile semiconductor memory element (memory cell) 504 is turned off because electrons are injected and the threshold value is increased.

  Here, the source S and the source SB are commonly connected in addition to the selected storage unit, that is, when 500-1 is selected, the gate signals CG1 and CG1B of 500-2 to 500-m are: It is set as high as about 4 V to prohibit writing and erasing to the memory element.

Next, this memory element is read.
When “0” is read, the gate signal SEL1 of the transfer gate is set to H (High) to turn on 501 and 503, and the gate signals CG1 and CG1B are set to about 0 v or 1 v. The sources S and SB are set to 0v. Since the threshold value 502 is high and off, and the threshold value 504 is low and on, the signal line D becomes “1” and the signal line DB becomes “0”. Here, when the gate signal SEN is set to H to activate the sense amplifier 400, the level of the signal lines D and DB is sensed and amplified by the sense amplifier 400, and the levels of the signal lines SO and SOB are “0”. Set to “1”. This signal is amplified by the main amplifier 300 to output the output OUT. In the case of “1” reading, the operation is the same except that the data is reversed.

  FIG. 19 shows a fifth embodiment of the nonvolatile semiconductor memory device of the present invention. FIG. 19 shows an embodiment in which a memory cell array of a nonvolatile semiconductor memory device is configured by arranging m storage units 700-1 to 700-m in one column.

  In the nonvolatile semiconductor memory device shown in FIG. 19, the main amplifier 300 and the sense amplifier 400 are the same as those in the example shown in FIG. 14.

  In the nonvolatile semiconductor memory device shown in FIG. 19, a column selection signal COLi is output from a column decoder (not shown) to a transfer gate unit composed of the transistors 601 and 602. i is 1 ≦ i ≦ n. The transistors 601 and 602 serve as column transfer gates. A column selection signal COLi is connected to the gate of the transistors 601 and 602, and the column selector gate is selected by the column selection signal COLi.

  The storage unit 700-1 includes memory cells 701 and 702 which are nonvolatile semiconductor memory elements according to the present invention. A word line WL1 output from a row decoder (not shown) is connected to the gate of the memory cell 701, and a word line WL1B output from a row decoder (not shown) is connected to the memory cell 702. The source of the memory cell 701 is connected to the signal line S, and the source of the memory cell 702 is connected to the signal line SB. The drain of the memory cell 701 is connected to the transistor 601 in the transfer gate portion through the common data line D, and the drain of the memory cell 702 is connected to the transistor 602 in the transfer gate portion through the common data line DB.

  Similarly, word lines WL2 and WL2B are connected to the memory cells in the storage unit 700-2, and the sources of the memory cells are connected to the source lines S and SB, respectively. Similarly, word lines WLm and WLmB are connected to the storage unit 500-m, and sources are connected to the source lines S and SB, respectively.

  The aforementioned sense amplifier corresponds to the sense amplifier 400, the aforementioned first nonvolatile semiconductor memory element corresponds to the transistor (memory cell) 701, and the second nonvolatile semiconductor memory element corresponds to the transistor (memory cell) 702. Corresponds. The above-described transfer gate portion corresponds to the transistors 601 and 602. In addition, the first transfer gate of the above-described transfer gate portion corresponds to the transistor 601, and the second transfer gate corresponds to the transistor 602. The first source line S described above corresponds to the source line S, and the second source line SB described above corresponds to the source line SB. The first word line WLn corresponds to the word lines WL1 to WLn, and the second word line WLnB corresponds to the word lines WL1B to WLnB. The first data line D corresponds to the common data line D, and the second data line corresponds to the common data line DB.

  The operation of this memory array is shown in FIG. In FIG. 20, the operation of the memory cell of the memory portion 700-1 is shown as an example.

  Referring to FIG. 20, writing is performed by setting column selection signal COLi to 0v, turning off transfer gate transistors 601 and 602, setting word line WL1 to 2v, word line WL1B to -2v, source S to 9v, and source SB to 7v. Set. In the memory cell 701, electron injection by hot electrons occurs, and in hole 702, hole injection by hot holes occurs.

  On the contrary, when erasing is performed on the word line WL1 at -2v, the word line WL1B at 2v, the source S at 7v, and the source SB at 9v, holes are injected at 702 and electrons are injected at 704. Note that, for example, 4 v is applied to the word lines WL1 and WLB so that writing and erasing do not occur in the storage units 700-2 to 700-m.

  At the time of reading, 2v is applied to the selected word lines WL1 and WL1B, and −2v is applied to the unselected word lines. When the selected column COLi is selected and turned on (H), in the case of “0” reading, the signal line D becomes “1” and the signal line DB becomes “0”. Here, the transistor 405 in the sense amplifier 400 The gate signal SEN becomes H (ON), the signal of the sense amplifier 400 is determined, the signal line SO becomes “0”, and the signal line SOB becomes “1”. The reading of “1” data is the same.

  FIG. 21 shows a sixth embodiment of the nonvolatile semiconductor memory device of the present invention. FIG. 21 shows an example in which n memory cells shown in FIG. 19 are specifically arranged in the column direction.

  In the example shown in FIG. 21, m × n storage units indicated by storage units 701-11 to 700-mn are arranged, the row direction is selected by word lines WL1 to WLm, and word lines WL1B to WLmB, and the column direction is selected. Are selected by the column selection signals SEL1 to SELn. The operations of the main amplifier 300 and the sense amplifier 400 are the same as those described with reference to FIG. The write, erase, and read operations are the same.

  Although the embodiments of the present invention have been described above, the nonvolatile semiconductor memory element and the nonvolatile semiconductor memory device of the present invention are not limited to the above illustrated examples, and do not depart from the gist of the present invention. Of course, various changes can be made within the range.

  According to the present invention, when erasing stored charges in a memory cell of a nonvolatile semiconductor memory device, the threshold value of the memory cell can be controlled to be on the positive side without using a complicated control circuit. A nonvolatile semiconductor memory element and a nonvolatile semiconductor memory device that can be manufactured by a CMOS process can be provided. Furthermore, it is possible to easily store and erase charges in the floating gate of the nonvolatile semiconductor memory element (memory cell) constituting the nonvolatile semiconductor memory device, and to erase the charge accumulated in the floating gate. To provide a nonvolatile semiconductor memory element that can easily control a threshold and can be manufactured by using a floating gate of one-layer polysilicon, and a nonvolatile semiconductor memory device including the nonvolatile semiconductor memory element. it can.

  DESCRIPTION OF SYMBOLS 1 ... N-type well formed in p-type semiconductor substrate, 2 ... n + diffusion region, 3 ... Floating gate, 4 ... Drain (n + type diffusion layer), 5 ... Source (N + type diffusion layer), 6 ... transistor gate, 11 ... control gate, Psub ... p-type semiconductor substrate, CG ... control gate, FG ... floating gate, D ... Drain, S ... Source, C (FC) ... Capacitor between control gate CG and floating gate FG, Tr ... Transistor (FET), 100 ... Memory cell array, 200 ... Source control Circuit 201 ... Nch transistor 202 ... Pch transistor

Claims (12)

A floating gate type nonvolatile semiconductor memory device comprising a floating gate disposed on an FET formed on a semiconductor substrate, a control gate for applying a gate voltage to the floating gate, a source and a drain,
At the time of charge accumulation in the floating gate, a first low voltage is applied to the control gate and a first high voltage is applied to the drain, or a first low voltage is applied to the control gate and the Applying a first high voltage to the source, generating hot electrons by band-to-band in the semiconductor substrate, injecting and accumulating charges in the floating gate;
When erasing charges accumulated in the floating gate, a second low voltage is applied to the control gate and a second high voltage is applied to the drain, or a second low voltage is applied to the control gate And applying a second high voltage to the source to generate a band-to-band hot hole in the semiconductor substrate, erasing the charge accumulated in the floating gate by the hot hole ,
The first high voltage is higher than the second high voltage, and the first low voltage is higher than the second low voltage (second low voltage <first low voltage <second high voltage < First high voltage),
The absolute value of the first high voltage is larger than the absolute value of the first low voltage, and the absolute value of the second high voltage is larger than the absolute value of the second low voltage (| first low voltage | <| First high voltage |, | second low voltage | <| second high voltage |),
The second low voltage is a negative low voltage, and when erasing the charge accumulated in the floating gate, a negative low voltage is applied to the control gate, whereby the second low voltage is applied between the control gate and the source. And a non-volatile semiconductor memory device controlled to have a negative threshold . The nonvolatile semiconductor memory device according to claim 1 , wherein the nonvolatile semiconductor memory device has a floating gate having a one-layer polysilicon structure. Arranged by arranging a plurality of floating gate type nonvolatile semiconductor memory elements each including a floating gate disposed on an FET formed on a semiconductor substrate, a control gate for applying a gate voltage to the floating gate, and a source and a drain A non-volatile semiconductor memory device,
The nonvolatile semiconductor memory element is
When charge is accumulated in the floating gate, a first low voltage is applied to the control gate, a first high voltage is applied to the source, and hot electrons due to band-to-band are applied to the semiconductor substrate. Generated inside, injected and accumulated in the floating gate,
When erasing charges accumulated in the floating gate, a second low voltage is applied to the control gate, a second high voltage is applied to the source, and hot holes due to band-to-band are generated. The charge generated in the semiconductor substrate and accumulated in the floating gate by the hot hole is erased (second low voltage <first low voltage <second high voltage <first High voltage , | first low voltage | <| first high voltage |, | second low voltage | <| second high voltage | ),
Furthermore, the second low voltage is a negative low voltage, the at the time of erasing of the floating gate stored charge to have a negative threshold between the control gate and the source, the negative to the control gate A non-volatile semiconductor memory device to which the second low voltage is applied. A nonvolatile semiconductor memory device comprising a first nonvolatile semiconductor memory element and a second nonvolatile semiconductor memory element,
The first and second nonvolatile semiconductor memory elements are:
A floating gate disposed on a FET formed on a semiconductor substrate, a control gate for applying a gate voltage to the floating gate, and a floating gate type nonvolatile semiconductor memory device including a source and a drain,
When charge is accumulated in the floating gate, a first low voltage is applied to the control gate, a first high voltage is applied to the source, and hot electrons due to band-to-band are applied to the semiconductor substrate. Generated inside, injected and accumulated in the floating gate,
When erasing charges accumulated in the floating gate, a second low voltage is applied to the control gate, a second high voltage is applied to the source, and hot holes due to band-to-band are generated. The charge generated in the semiconductor substrate and accumulated in the floating gate by the hot hole is erased (second low voltage <first low voltage <second high voltage <first High voltage , | first low voltage | <| first high voltage |, | second low voltage | <| second high voltage | ),
Further, the second low voltage is a negative low voltage, and when erasing charges accumulated in the floating gate, a negative threshold is applied to the control gate so as to have a negative threshold between the control gate and the source. Applying the second low voltage of a low voltage of
A source of the first nonvolatile semiconductor memory element and a source of the second nonvolatile semiconductor memory element are connected in common;
A drain of the first nonvolatile semiconductor memory element and a first transfer gate are connected; a drain of the second nonvolatile semiconductor memory element and a second transfer gate are connected;
When reading data from the first and second nonvolatile semiconductor memory elements, a predetermined value is applied to each of the control gate of the first nonvolatile semiconductor memory element and the control gate of the second nonvolatile semiconductor memory element. A nonvolatile semiconductor memory device that reads out an output signal from the drains of the first and second nonvolatile semiconductor memory elements while turning on the transfer gate. The nonvolatile semiconductor memory device includes an SRAM (Static Random Access Memory) that holds a signal by a flip-flop circuit,
The output signal from the first and second nonvolatile semiconductor memory elements is transferred to the flip-flop circuit through the transfer gate, and the signal transferred by the flip-flop circuit is held. the nonvolatile semiconductor memory device according to 4. A nonvolatile semiconductor memory device comprising a first nonvolatile semiconductor memory element and a second nonvolatile semiconductor memory element,
The first and second nonvolatile semiconductor memory elements are:
A floating gate disposed on a FET formed on a semiconductor substrate, a control gate for applying a gate voltage to the floating gate, and a floating gate type nonvolatile semiconductor memory device including a source and a drain,
When charge is accumulated in the floating gate, a first low voltage is applied to the control gate, a first high voltage is applied to the source, and hot electrons due to band-to-band are applied to the semiconductor substrate. Generated inside, injected and accumulated in the floating gate,
When erasing charges accumulated in the floating gate, a second low voltage is applied to the control gate, a second high voltage is applied to the source, and hot holes due to band-to-band are generated. The charge generated in the semiconductor substrate and accumulated in the floating gate by the hot hole is erased (second low voltage <first low voltage <second high voltage <first High voltage , | first low voltage | <| first high voltage |, | second low voltage | <| second high voltage | ),
Further, the second low voltage is a negative low voltage, and when erasing charges accumulated in the floating gate, a negative threshold is applied to the control gate so as to have a negative threshold between the control gate and the source. Applying the second low voltage of a low voltage of
The source of the first nonvolatile semiconductor memory element is connected to the first source line SL, the source of the second nonvolatile semiconductor memory element is connected to the second source line SR,
A drain of the first nonvolatile semiconductor memory element and a first transfer gate are connected; a drain of the second nonvolatile semiconductor memory element and a second transfer gate are connected;
When reading data from the first and second nonvolatile semiconductor memory elements, a predetermined value is applied to each of the control gate of the first nonvolatile semiconductor memory element and the control gate of the second nonvolatile semiconductor memory element. A nonvolatile semiconductor memory device that reads out an output signal from the drains of the first and second nonvolatile semiconductor memory elements while turning on the transfer gate. The nonvolatile semiconductor memory device includes an SRAM (Static Random Access Memory) that holds a signal by a flip-flop circuit,
The nonvolatile memory according to claim 6 , wherein output signals from the first and second nonvolatile semiconductor memory elements are transferred to the flip-flop circuit through the transfer gate, and the signals transferred by the flip-flop circuit are held. Semiconductor memory device. A power supply line to a flip-flop circuit in the SRAM is connected to a power supply via a power switch transistor, and the power supply line is applied to the flip-flop circuit by controlling on / off of the power switch transistor. Item 8. The nonvolatile semiconductor memory device according to Item 7 . A plurality of storage units including a first nonvolatile semiconductor memory element and a second nonvolatile semiconductor memory element are arranged, and outputs from the first and second nonvolatile semiconductor memory elements in the selected storage unit A nonvolatile semiconductor memory device comprising a sense amplifier for inputting a signal and amplifying the input signal,
The first and second nonvolatile semiconductor memory elements are:
A floating gate disposed on a FET formed on a semiconductor substrate, a control gate for applying a gate voltage to the floating gate, and a floating gate type nonvolatile semiconductor memory device including a source and a drain,
When charge is accumulated in the floating gate, a first low voltage is applied to the control gate, a first high voltage is applied to the source, and hot electrons due to band-to-band are applied to the semiconductor substrate. Generated inside, injected and accumulated in the floating gate,
When erasing charges accumulated in the floating gate, a second low voltage is applied to the control gate, a second high voltage is applied to the source, and hot holes due to band-to-band are generated. The charge generated in the semiconductor substrate and accumulated in the floating gate by the hot hole is erased (second low voltage <first low voltage <second high voltage <first High voltage , | first low voltage | <| first high voltage |, | second low voltage | <| second high voltage | ),
Further, the second low voltage is a negative low voltage, and when erasing charges accumulated in the floating gate, a negative threshold is applied to the control gate so as to have a negative threshold between the control gate and the source. Applying the second low voltage of a low voltage of
The first nonvolatile semiconductor memory element, the drain, and the first transfer gate are connected in each storage unit, and the drain and the second transfer gate of the second nonvolatile semiconductor memory element are connected. ,
The sources of the first nonvolatile semiconductor memory elements in each storage unit are commonly connected to a first source line S, and the sources of the second nonvolatile semiconductor memory elements are commonly connected to a second source line SB.
The sense amplifier includes a latch circuit in which the gates of the pair of transistors are connected to the drain of the counterpart,
The output of the first transfer gate in each storage unit is connected in common to the gate of one transistor of the latch circuit of the sense amplifier, and the output of the second transfer gate is connected to the other transistor of the latch circuit of the sense amplifier. Commonly connected to the gate
The gate of the first non-volatile semiconductor memory element in each storage unit is connected to the first control gate line CGn, and the gate of the second non-volatile semiconductor memory element is connected to the second control gate line CGnB. Connected,
When a desired storage unit is selected from the plurality of storage units, the transfer gate in the desired storage unit is turned on, and the first and second control gate lines CGn and CGnB corresponding to the storage unit are set. A nonvolatile semiconductor memory device that, when activated, transfers output signals from the first and second nonvolatile semiconductor memory elements to a latch circuit in the sense amplifier via the transfer gate. A nonvolatile semiconductor memory device comprising a first nonvolatile semiconductor memory element and a second nonvolatile semiconductor memory element,
The first nonvolatile semiconductor memory element and the second nonvolatile semiconductor memory element include a floating gate disposed on an FET formed on a semiconductor substrate, a control gate for applying a gate voltage to the floating gate, a source, It is composed of a floating gate type nonvolatile semiconductor memory device having a drain,
When charge is accumulated in the floating gate, a first low voltage is applied to the control gate, a first high voltage is applied to the source, and hot electrons due to band-to-band are applied to the semiconductor substrate. Generated inside, injected and accumulated in the floating gate,
When erasing charges accumulated in the floating gate, a second low voltage is applied to the control gate, a second high voltage is applied to the source, and hot holes due to band-to-band are generated. The charge generated in the semiconductor substrate and accumulated in the floating gate by the hot hole is erased (second low voltage <first low voltage <second high voltage <first High voltage , | first low voltage | <| first high voltage |, | second low voltage | <| second high voltage | ),
Further, the second low voltage is a negative low voltage, and when erasing charges accumulated in the floating gate, a negative threshold is applied to the control gate so as to have a negative threshold between the control gate and the source. Applying the second low voltage of a low voltage of
The source of the first nonvolatile semiconductor memory element is connected to the first source line S, the source of the second nonvolatile semiconductor memory element is connected to the second source line SB,
The gate of the first nonvolatile semiconductor memory element is connected to a first word line WLn, the gate of the second nonvolatile semiconductor memory element is connected to a second word line WLnB,
A non-volatile semiconductor memory device in which a drain of the first non-volatile semiconductor memory element is connected to a first data line D, and a drain of the second non-volatile semiconductor memory element is connected to a second data line DB. A plurality of storage units including a first nonvolatile semiconductor memory element and a second nonvolatile semiconductor memory element are arranged, and output signals from the first and second nonvolatile semiconductor memory elements in the selected storage unit A nonvolatile semiconductor memory device including a sense amplifier that inputs a signal through a transfer gate unit driven by a column selection signal and amplifies the input signal,
The first and second nonvolatile semiconductor memory elements are:
A floating gate disposed on a FET formed on a semiconductor substrate, a control gate for applying a gate voltage to the floating gate, and a floating gate type nonvolatile semiconductor memory device including a source and a drain,
When charge is accumulated in the floating gate, a first low voltage is applied to the control gate, a first high voltage is applied to the source, and hot electrons due to band-to-band are applied to the semiconductor substrate. Generated inside, injected and accumulated in the floating gate,
When erasing charges accumulated in the floating gate, a second low voltage is applied to the control gate, a second high voltage is applied to the source, and hot holes due to band-to-band are generated. The charge generated in the semiconductor substrate and accumulated in the floating gate by the hot hole is erased (second low voltage <first low voltage <second high voltage <first High voltage , | first low voltage | <| first high voltage |, | second low voltage | <| second high voltage | ),
Further, the second low voltage is a negative low voltage, and when erasing charges accumulated in the floating gate, a negative threshold is applied to the control gate so as to have a negative threshold between the control gate and the source. Applying the second low voltage of a low voltage of
Further, the source of the first nonvolatile semiconductor memory element in each storage unit is commonly connected to the first source line S, and the source of the second nonvolatile semiconductor memory element is commonly connected to the second source line SB. And
Further, the drain of the first nonvolatile semiconductor memory element in each storage section is commonly connected to the first transfer gate of the transfer gate section, and the drain of the second nonvolatile semiconductor memory element is connected to the transfer gate section. Connected in common to the second transfer gate,
The gate of the first nonvolatile semiconductor memory element in each storage unit is connected to a first word line WLn for selecting the nonvolatile semiconductor memory element, and the gate of the second nonvolatile semiconductor memory element is Connected to a second word line WLnB for selecting the nonvolatile semiconductor memory element;
When selecting a desired storage unit from the plurality of storage units, the first word line WLn and the second word line WLnB in the selected storage unit are activated, and the first and second transfer gates are activated. A nonvolatile semiconductor memory device that transfers output signals from the first and second nonvolatile semiconductor memory elements of the storage unit to the sense amplifier by turning on the signal.   A floating gate type nonvolatile semiconductor memory device comprising a floating gate disposed on an FET formed on a semiconductor substrate, a control gate for applying a gate voltage to the floating gate, a source and a drain,
  At the time of charge accumulation in the floating gate, a first low voltage is applied to the control gate and a first high voltage is applied to the drain, or a first low voltage is applied to the control gate and the Applying a first high voltage to the source, generating hot electrons by band-to-band in the semiconductor substrate, injecting and accumulating charges in the floating gate;
  When erasing charges accumulated in the floating gate, a second low voltage is applied to the control gate and a second high voltage is applied to the drain, or a second low voltage is applied to the control gate And applying a second high voltage to the source to generate a band-to-band hot hole in the semiconductor substrate, erasing the charge accumulated in the floating gate by the hot hole,
  The first high voltage is higher than the second high voltage, and the first low voltage is higher than the second low voltage (second low voltage <first low voltage <second high voltage < First high voltage),
  The absolute value of the first high voltage is larger than the absolute value of the first low voltage, and the absolute value of the second high voltage is larger than the absolute value of the second low voltage (| first low voltage | <| First high voltage |, | second low voltage | <| second high voltage |),
  The second low voltage is a positive low voltage, and when erasing the charge accumulated in the floating gate, a positive low voltage is applied to the control gate, thereby causing a gap between the control gate and the source. A non-volatile semiconductor memory device that is controlled to have a positive threshold.

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