摘要:
A NAND-cell type EEPROM having a plurality of bit lines, a plurality of control gate lines intersecting with the bit lines, and a plurality of memory cells driven by applying a potential to the control gate lines for selectively storing data, supplying data to the bit lines and receiving data therefrom. The memory cells form a plurality of cell units. The memory cells constituting each cell unit are connected in series to one bit line by a common selecting gate transistor. A plurality of data latch circuits are provided on the bit lines, respectively, for storing data to be written into the memory cells selected by the control gate lines. Further, a plurality of selecting gate drivers are provided to correspond to the cell units, respectively, for driving the control gate lines. A row decoder decodes row addresses for driving the selecting gate drivers and the control gate lines. A plurality of block-address latch circuits are provided to correspond to the selecting gate drivers, respectively, for temporarily storing signals derived from a row address by the row decoder, thereby to select at least two of the selecting gate drivers at the same time in order to write data.
摘要:
A NAND cell type EEPROM has parallel data transmission lines formed above a substrate, and a memory cell section including a plurality of NAND type cell units containing a NAND type cell unit that is associated with a certain bit line of the bit lines. This NAND type cell unit has a series-circuit of a preselected number of data storage transistors with control gates, and a selection transistor. A substrate voltage-stabilizing layer is insulatively provided above the substrate and positioned in the field area in adjacent to the certain bit line. The conductive layer is connected to the substrate by a contact portion so that the substrate voltage can be constantly set to a preselected voltage potential of a fixed value during the NAND type cell unit is being subjected to the write and erase modes.
摘要:
An electrically erasable programmable read-only memory with a NAND cell structure has parallel bit lines, and memory cells defining NAND cell blocks, each of which has a series-circuit of memory cell transistors. Each transistor has a floating gate and a control gate. Parallel word lines are connected to the control gates of the cell transistors. The first, second and third intermediate voltages are used in the data write mode: the first voltage is lower than the "H" level voltage and higher than the "L" level voltage; the second and third voltages are higher than the first voltage and lower than the "H" level voltage. Data is written into a selected memory cell transistor of a NAND cell block, by applying the "H" level voltage to a word line connected to the selected transistor, applying the second voltage to the remaining unselected word lines, applying a corresponding bit line associated with the selected transistor with one of the first and third voltages which is selected in accordance with a logic level of the data, and applying unselected bit lines with the third voltage, whereby carriers are moved by tunneling from or to the floating gate of the selected memory cell transistor.
摘要:
An electrically erasable programmable read-only memory with a NAND cell structure has parallel bit lines, and memory cells defining NAND cell blocks, each of which has a series-circuit of memory cell transistors. Each transistor has a floating gate and a control gate. Parallel word lines are connected to the control gates of the cell transistors. The first, second and third intermediate voltages are used in the data write mode: the first voltage is lower than the "H" level voltage and higher than the "L" level voltage; the second and third voltages are higher than the first voltage and lower than the "H" level voltage. Data is written into a selected memory cell transistor of a NAND cell block, by applying the "H" level voltage to a word line connected to the selected transistor, applying the second voltage to the remaining unselected word lines, applying a corresponding bit line associated with the selected transistor with one of the first and third voltages which is selected in accordance with a logic level of the data, and applying unselected bit lines with the third voltage, whereby carriers are moved by tunneling from or to the floating gate of the selected memory cell transistor.
摘要:
An EEPROM for storing multi-level data includes a memory cell array in which electrically erasable and programmable memory cells are arranged in matrix and each of the memory cells has at least three storage states, a write circuit for writing data to the memory cells, first and second write verify means each constituted of a sense amplifier, a data latch circuit and a detection circuit, for verifying an insufficient-written state of a memory cell and an excess-written state of a memory cell, respectively, an additional write circuit for additionally writing data to the memory cell in the insufficient-written state, and an additional erase circuit for additionally erasing data from the memory cell in the excess-written state.
摘要:
An EEPROM includes an array of memory cell transistors, which is divided into cell blocks each including NAND cell units of series-connected cell transistors. A sense amplifier is connected to bit lines and a comparator. A data-latch circuit is connected to the comparator, for latching a write-data supplied from a data input buffer. After desired cell transistors selected for programming in a selected block are once programmed, a write-verify operation is performed. The comparator compares the actual data read from one of the programmed cell transistors with the write-data, to verify its written state. The write-verify process checks the resulting threshold voltage for variations using first and second reference voltages defining the lower-limit and upper-limit of an allowable variation range. If the comparison results under employment of the first voltage shows that an irregularly written cell transistor remains with an insufficient threshold voltage which is so low as to fail to fall within the range, the write operation continues for the same cell transistor. If the comparison results under employment of the second voltage shows that an excess-written cell transistor remains, the block is rendered "protected" at least partially.
摘要:
An EEPROM includes an array of memory cell transistors, which is divided into cell blocks each including NAND cell units of series-connected cell transistors. A sense amplifier is connected to bit lines and a comparator. A data-latch circuit is connected to the comparator, for latching a write-data supplied from a data input buffer. After desired cell transistors selected for programming in a selected block are once programmed, a write-verify operation is performed. The comparator compares the actual data read from one of the programmed cell transistors with the write-data, to verify its written state. The write-verify process checks the resulting threshold voltage for variations using first and second reference voltages defining the lower-limit and upper-limit of an allowable variation range. If the comparison results under employment of the first voltage shows that an irregularly written cell transistor remains with an insufficient threshold voltage which is so low as to fail to fall within the range, the write operation continues for the same cell transistor. If the comparison results under employment of the second voltage shows that an excess-written cell transistor remains, the block is rendered "protected" at least partially.
摘要:
An EEPROM includes an array of memory cell transistors, which is divided into cell blocks each including NAND cell units of series-connected cell transistors. A sense amplifier is connected to bit lines and a comparator. A data-latch circuit is connected to the comparator, for latching a write-data supplied from a data input buffer. After desired cell transistors selected for programming in a selected block are once programmed, a write-verify operation is performed. The comparator compares the actual data read from one of the programmed cell transistors with the write-data, to verify its written state. The write-verify process checks the resulting threshold voltage for variations using first and second reference voltages defining the lower-limit and upper-limit of an allowable variation range. If the comparison results under employment of the first voltage shows that an irregularly written cell transistor remains with an insufficient threshold voltage which is so low as to fail to fall within the range, the write operation continues for the same cell transistor. If the comparison results under employment of the second voltage shows that an excess-written cell transistor remains, the block is rendered "protected" at least partially.
摘要:
A semiconductor memory comprises: a first conductivity type semiconductor substrate and memory cells each constituted of an island-like semiconductor layer, a charge storage layer and a control gate, the charge storage layer and the control gate being formed to entirely or partially encircle a sidewall of the island-like semiconductor layer, wherein the memory cells are disposed in series, and the island-like semiconductor layer on which the memory cells are disposed has cross-sectional areas in a horizontal direction which vary stepwise.
摘要:
A semiconductor memory comprises: a substrate; and one or more memory cells constituted of at least one island-like semiconductor layer, a charge storage layer and a control gate, the charge storage layer and the control gate being formed to entirely or partially encircle a sidewall of the island-like semiconductor layer, wherein at least one of said one or more memory cells is electrically insulated from the semiconductor substrate and has an insulating film allowing an electric charge to pass at least in a part of a region between the charge storage layer and the island-like semiconductor layer.