Chuo University

Kosuke Miyaji

Ken Takeuchi

Tomoko Iwasaki

Chao Sun

To improve a reading speed and a writing speed while preventing occurrence of disturbance in a resistance storage element, specifically, a nonvolatile storage device that has a memory having at least one nonvolatile resistance storage element and a control unit configured to write a high resistance state or a low resistance state to the resistance storage element, wherein the control unit applies a bias to the resistance storage element in a verification operation carried out after writing the high resistance state, or applies a bias to the resistance storage element in a verification operation carried out after writing the low resistance state, these biases being in directions opposite to each other.

Nonvolatile storage device and method of controlling the same

To reduce deterioration of non-volatile memory and write data at higher speed, writing data is stored in a ReRAM when a page utilization rate R is lower than a threshold Rthand/or the writing data is frequently-rewritten data. With an empty space Sempin the ReRAM being less than a threshold Sth (step S), when the data in the ReRAM is infrequently-rewritten data and the page utilization rate R obtained if target data is stored in a flash memoryis equal to or higher than a threshold value Rth(steps Sand S), data of logical sectors contained in N logical page addresses stored in a transfer list is read from the ReRAM to be written to the flash memory (steps Sto S). These steps reduce deterioration of the flash memory and allow higher data writing.

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Tokyo, Japan

Kosuke Miyaji