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Patent Issued for Nonvolatile Storage Device Having a Plurality of Plate Electrodes

February 12, 2014



By a News Reporter-Staff News Editor at Electronics Newsweekly -- A patent by the inventors Yoshihara, Hiroshi (Nagasaki, JP); Arima, Takayuki (Nagasaki, JP); Etou, Takeshi (Nagasaki, JP), filed on January 19, 2011, was published online on January 28, 2014, according to news reporting originating from Alexandria, Virginia, by VerticalNews correspondents.

Patent number 8638616 is assigned to Sony Corporation (Tokyo, JP).

The following quote was obtained by the news editors from the background information supplied by the inventors: "In general, the present invention relates to a nonvolatile storage device. To put it in detail, the present invention relates to a nonvolatile storage device having a plurality of plate electrodes each used for applying a voltage to a plurality of memory cells.

"Most of information apparatus such as a computer make use of a high-density DRAM (Dynamic Random Access Memory) as a storage device which is capable of operating at a high speed. Since the DRAM is a volatile storage device which inevitably loses information stored therein when the power supply thereof is turned off, however, there is a demand for a nonvolatile storage device which does not undesirably lose information stored therein even if the power supply thereof is turned off.

"In order to meet the demand described above, there has been proposed a variable-resistance-type storage device to be used as the nonvolatile storage device. Typical examples of the variable-resistance-type storage device are an FeRAM (Ferroelectric Random Access Memory), an MRAM (Magnetic Random Access Memory), a PMC (Programmable Metallization Cell) and an RRAM (Resistive Random Access Memory). Each of these nonvolatile storage devices is capable of continuously holding information stored therein for long time even if the supply of power to the nonvolatile storage device is cut off. In addition, each of these nonvolatile storage devices does not require a refresh operation so that the amount of power supplied to the storage device can be reduced by a quantity which is needed to carry out the refresh operations.

"Such nonvolatile storage devices include one that adopts a plate method. In the nonvolatile storage device which adopts the plate method, a storage element employed in each memory cell included in the nonvolatile storage device is electrically connected to a common plate electrode for applying a common voltage to the storage elements. The plate electrode provides a storage element with a voltage for writing data into a memory cell employing the storage element or a voltage for erasing data from a memory cell employing the storage element. For more information on this nonvolatile storage device which adopts the plate method, the reader is advised to refer to Japanese Patent Laid-open No. 2006-351779."

In addition to the background information obtained for this patent, VerticalNews journalists also obtained the inventors' summary information for this patent: "The nonvolatile storage device adopting the plate method as described above has a merit that the process of manufacturing the nonvolatile storage device is simple. On the other hand, the nonvolatile storage device adopting the plate method as described above has a demerit that the circuit of the plate electrode needs to make a transition from a voltage for writing data into a memory cell employing the storage element to a voltage for erasing data from a memory cell employing the storage element and vice versa. Thus, the power consumption raises a problem. In particular, if the memory capacity of the nonvolatile storage device is increased, the area of the plate electrode also undesirably rises so that the amount of power consumed during operations to electrically charge and discharge the plate electrode further increases unavoidably.

"Addressing the problems described above, inventors of the present invention have provided a plate-method nonvolatile storage device capable of reducing the power consumption.

"In order to solve the problems described above, according to an embodiment of the present invention, there is provided a nonvolatile storage device which employs:

"a plurality of memory mats each including a plurality of memory cells;

"a plurality of plate electrodes each provided for every individual one of the memory mats and each used for applying a voltage to the memory cells;

"a power-supply section configured to apply a voltage to each of the plate electrodes;

"a switch circuit having a plurality of switches provided between the power-supply section and each of the plate electrodes and between the plate electrodes; and

"a control section configured to control the switch circuit in order to disconnect the plate electrodes from the power-supply section and to connect the plate electrodes to each other in order to carry out electrical charging and discharging operations among the plate electrodes.

"In addition, in the nonvolatile storage device according to the embodiment of the present invention, the control section controls the switch circuit in order to connect a specific one of the plate electrodes to another one of the plate electrodes so as to transfer electric charge accumulated in the specific plate electrode to the other plate electrode and in order to connect the specific plate electrode to the other plate electrode later on so as to transfer electric charge accumulated in the other plate electrode to the specific plate electrode.

"On top of that, in the nonvolatile storage device according to the embodiment of the present invention, the control section controls the switch circuit in order to connect a specific one of the plate electrodes to a plurality of other ones of the plate electrodes in an order determined in advance so as to transfer electric charge accumulated in the specific plate electrode to the other plate electrodes and in order to connect the specific plate electrode to the other plate electrodes on in a reverse order opposite to the order determined in advance so as to transfer electric charge accumulated in the other plate electrodes to the specific plate electrode.

"In addition, in the nonvolatile storage device according to the embodiment of the present invention, each individual one of the memory cells employs a variable-resistance-type storage element and an access transistor connected to one of the two terminals of the variable-resistance-type storage element. The other terminal of the variable-resistance-type storage element is connected to the plate electrode.

"According to the present invention, in the plate-method nonvolatile storage device, electric charge accumulated in a plate electrode is reutilized so that the magnitude of a consumed current can be reduced. In particular, by increasing the number of memory mats each provided with a plate electrode, the effect of the reduced magnitude of the consumed power is big."

URL and more information on this patent, see: Yoshihara, Hiroshi; Arima, Takayuki; Etou, Takeshi. Nonvolatile Storage Device Having a Plurality of Plate Electrodes. U.S. Patent Number 8638616, filed January 19, 2011, and published online on January 28, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=42&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=2062&f=G&l=50&co1=AND&d=PTXT&s1=20140128.PD.&OS=ISD/20140128&RS=ISD/20140128

Keywords for this news article include: Electronics, Sony Corporation, Random Access Memory.

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Source: Electronics Newsweekly


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