Storage device drive method

Abstract

Provided is a method for driving a storage device which can improve reliability of data write-in in a storage device including a variable resistance element. When writing data, write-in pulses of different shapes are applied between two electrodes (21, 24) of the variable resistance element (2) a plurality of times. Since it is possible to eliminate diffusion loss of a conductive path by self heating (Jour heat) of the variable resistance element (2), the data holding operation after the write-in is stabilized.Moreover, it is possible to eliminate destruction of the variable resistance element (2) when performing a sufficient write-in operation. Accordingly, it is possible to stabilize the data write-in operation.

Description

technical field [0001] The present invention relates to a method of driving the memory device when changing the variable resistance element from a high resistance state to a low resistance state (writing operation) in a memory device having a memory cell constituted by a nonvolatile variable resistance element . Background technique [0002] Conventional storage devices, especially those using flash memory, have been widely used in recent years because they do not require power to hold stored data. Especially in portable terminal devices including mobile phone units, flash memory is commonly used as memory. However, a storage device using such a flash memory has a problem of slow data writing speed (see, for example, Non-Patent Document 1). [0003] Therefore, the present applicant has previously proposed a memory device using a nonvolatile variable resistance element having superior characteristics to those of the above-mentioned flash memory (for example, Patent Document...

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Problems solved by technology

[0007] However, in the variable resistance element described above, depending on the structure or manufacturing method of the insulating film and the conductive film, in the low resistance state after writing, there may be cases where the fluctuation of the resistance is large.

If the fluctuation of the resistance is large like this, it is difficult to hold the written data stably

[0008] In addition, in order to perform writing sufficiently without causing a writing error, etc., it is necessary to increase the voltage applied to the variable resistance element, or to increase the current flowing through the variable resistance element, or to lengthen the voltage application time.

However, if a high voltage exceeding the necessary value is applied to the varistor element or an excessively large current flows, dielectric breakdown may occur in the insulating film, and the varistor element itself may be destroyed.

[0009] In this way, in conventional memory devices, it is difficult to stably write and hold data, and therefore it is difficult to improve reliability.

There is room for improvement in the above-mentioned device

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