Kabushiki Kaisha Toshiba

Yasuhiko Honda

Masao Kuriyama

Hideo Kato

Hidetoshi Saito

Tokumasa Hara

Takafumi Ikeda

Tatsuya Hiramatsu

Yoshihiko Kamata

Takahiro Suzuki

Masaaki Kuwagata

Gyosho Chin

Masao Iwamoto

Kiyochika Kinjo

Ryu Hondai

Toru Tanzawa

Tadayuki Taura

Hitoshi Shiga

Akira Umezawa

Mario Sako

Noriyasu Kumazaki

Yoshinori Takano

Takayuki Harima

Tatsuro Midorikawa

Takamichi Kasai

Shinya Fujisawa

Jin Kashiwagi

Manabu Satoh

Yuji Komine

Jun Fujimoto

According to one embodiment, a semiconductor memory device includes a memory cell array including memory cells, each of which is arranged at a position of between a word line and a bit line, a row decoder, and a bit line control circuit. And when data is to be read out from the memory cell, a charge control circuit controls the gate voltages of a first transistor, a second transistor, a third transistor, and a fourth transistor, respectively, so that the bit line is charged in accordance with a first characteristic obtained by increasing a current driving capacity of the first transistor during a desired period after start of charge of the bit line, and the bit line is then charged in accordance with a second characteristic obtained by returning the current driving capacity of the first transistor to the lower current driving capacity after elapse of the desired period.

Semiconductor memory device with bit line charging circuit and control method thereof

A method for controlling a threshold value in a nonvolatile semiconductor memory device, includes: performing writing at least once on at least one of the memory cells to be adjusted to a state other than an erased state with an applied voltage that does not cause excess writing, with verify reading being not performed; and performing verify reading by applying a verify voltage corresponding to a target threshold value of the memory cell after the writing is performed on the at least one of the memory cells to be adjusted to the state other than the erased state, and, when the threshold value of the memory cell is determined to be lower than the target threshold value, repeating the writing with the applied voltage that does not cause excess writing and the verify reading until the threshold value of the memory cell becomes equal to or higher than the target threshold value.

Method for controlling threshold value in nonvolatile semiconductor memory device

According to one embodiment, a nonvolatile semiconductor memory device includes a memory cell transistor, a word line, a row decoder, a sense amplifier which determines the data in the memory cell transistor via the bit line, a first bit line clamp transistor connected in series between the bit line and the sense amplifier, a second bit line clamp transistor connected in parallel to the first bit line clamp transistor and having a current driving capability higher than that of the first bit line clamp transistor, and a bit line control circuit which turns on the first bit line clamp transistor and the second bit line clamp transistor using a common gate voltage during a predetermined period from a start of charge of the bit line, and turns off only the second bit line clamp transistor when the predetermined period has elapsed.

Nonvolatile semiconductor memory device

According to one embodiment, a semiconductor memory device includes a plurality of memory cells in which data can be rewritable, a plurality of bit lines connected to the plurality of memory cells, and a plurality of sense circuits that are connected to the plurality of bit lines, respectively, sense data written in the memory cells to perform a verify operation with the bit lines charged to first potentials, and charge a bit line, which is connected to a memory cell determined to be defective as a result of the verify operation, to the first potential in the verify operation.

Semiconductor memory device and control method thereof

A semiconductor storage apparatus has a control circuit. The control circuit deactivates the first and second amplifier circuits, turns off the first, second, fourth and fifth switch circuits, and turns on the third and sixth switch circuits in response to an external signal based on reduction of current dissipation of a power supply which supplies the power supply voltage.

Semiconductor storage apparatus including a pump circuit for the active mode and the standby mode

A NAND flash memory having a memory cell array formed of a plurality of blocks including memory cell transistors arranged in a matrix form. The NAND flash memory has a first bit line; a first sense amplifier connected to the first bit line, the first sense amplifier sensing or controlling a potential on the first bit line; a second bit line; and a second sense amplifier connected to the second bit line to sense or control a potential on the second bit line. The NAND flash memory has a first drain side selection gate line; a second drain side selection gate line; a third drain side selection gate line; a fourth drain side selection gate line; a first source side selection gate line; and a second source side selection gate line. The NAND flash memory has a first block; a second block; and a decoder which turns on one of the first and third drain side selection MOS transistors and turns off the other, and which turns on one of the third and fourth drain side selection MOS transistors and turns off the other.

NAND flash memory

A nonvolatile semiconductor memory includes a memory cell array, bit lines, a first voltage generator, and a second voltage generator. The memory cell array includes memory cells. The bit lines each of which is connected electrically to one end of the current path of the corresponding one of the memory cells. The first voltage generator which is capable of supplying via a first output terminal to the bit lines a first voltage externally supplied or a third voltage which is obtained by stepping down a second voltage supplied and higher than the first voltage and which is as high as the first voltage. The second voltage generator which is capable of supplying a fourth voltage obtained by stepping down the second voltage to the bit lines via a second output terminal when the first voltage generator steps down the second voltage to generate the third voltage.

Nonvolatile semiconductor memory with charge storage layers and control gates

A power circuit includes a reference potential circuit, a step-up circuit, and a conversion circuit. The reference potential circuit generates a reference potential. The step-up circuit generates a desired internal potential by stepping up a power supply potential. The step-up circuit includes a comparison circuit, a differential amplifier circuit, and a switch element. The comparison circuit outputs the result of comparison between a potential and the reference potential. The differential amplifier circuit is turned on or off by the operation control signal. The switch element performs on/off control according to the operation control signal and resets the output potential of the differential amplifier circuit. The conversion circuit converts the of the operation control signal so as to make longer the on period of the differential amplifier circuit and the off period of switch element.

Power circuit including step-up circuit and stabilizing method thereof

A nonvolatile semiconductor storage device capable of storing a plurality of bits of data in one memory cell by assigning multivalued data having a higher-order bit selected from one of a pair of data in a first unit and a lower-order bit selected from the other of the pair of data to each threshold voltage of the memory cell, wherein in a first write operation that processes data in the first unit, the logic of one of the higher-order bit and the lower-order bit is fixed, and two pieces of multivalued data that maximize the difference between the threshold voltages are assigned, thereby storing one bit of input data in the one memory cell in a pseudo binary state, and in a second write operation that processes data in a second unit larger than the first unit, a plurality of bits of input data is stored in the one memory cell in a multivalued state, and parity data for error correction in the second unit is stored in the memory cell.

Nonvolatile semiconductor storage device

A non-volatile semiconductor storage device includes a memory cell array having a plurality of non-volatile memory cells, an address search circuit which searches for write object data and outputs an address where the write object data is present, when writing data into the non-volatile memory cells, and a control circuit which exercises control to write the write object data into the non-volatile memory cells in accordance with the address output from the address search circuit.

Non-volatile semiconductor storage device with address search circuit used when writing

A semiconductor device comprises a board, a first semiconductor storage device placed on the board, and a second semiconductor storage device placed on the board. Each of the first and second semiconductor storage devices has a first pad for inputting a chip enable signal, a second pad for inputting a write enable signal, a third pad for inputting an output enable signal, a fourth pad for inputting an address signal, and a fifth pad for inputting data. The first semiconductor storage device has a sixth pad which is electrically connected to the first pad of the second semiconductor device, and the second semiconductor storage device has a seventh pad which is electrically connected to the first pad of the first semiconductor device.

Semiconductor device and method of controlling the same

A nonvolatile semiconductor memory includes a transistor, a first MOS, a second MOS, a first voltage circuit, and a second voltage circuit. The transistor includes a accumulation layer, a control gate, and a first impurity diffused layer. The first MOS includes a first electrode and a second layer. The second MOS includes a second electrode and a third layer, after the channels being formed, the first MOS and the second MOS being cut off. The first voltage circuit applies a first voltage to an active region to generate a forward bias. The second voltage circuit applies a second voltage, and a third voltage to the control gate of the transistor, after the first voltage circuit charges the first to third impurity diffused layer to the first voltage, the second voltage circuit applying the second voltage and the third voltage to the control gate of the transistor.

Nonvolatile semiconductor memory including charge accumulation layer and control gate

A semiconductor memory device includes a memory cell array which includes a plurality of memory cells which are arrayed in a matrix at intersections between a plurality of word lines and a plurality of bit lines and a power supply circuit which includes a first band gap reference circuit which outputs a first output voltage, and a second band gap reference circuit which outputs a second output voltage having lower temperature characteristics than the first output voltage on a low temperature side, and generates a power supply voltage on the basis of the second output voltage at a time of a data write operation of the memory cells.

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Hiratsuka, Japan

Yasuhiko Honda