1. Field of the Invention
The present invention relates to a storage device that is capable of performing a writing, a readout and an erasure of binary data (information) or data with more levels by changing electrical characteristics between two electrodes.
2. Description of the Related Art
In related art, a micro electronic programmable element as shown in FIGS. 12(A) and 12(B) is known as a storage element that may be formed easily with a simple structure (see Japanese Patent Application Publication 2002-536840). This element ionizes, by an application of a predetermined voltage, silver (Ag) contained in an inter-electrode material layer 103 between two electrodes 101 and 102, and forms, by a transfer of the ionized silver, an electron conduction path (channel) 104 that changes an electrical resistance between the above electrodes 101 and 102 to perform a writing of data.
In the element of related art, as a matter of convenience, a state in which a resistance between the two electrodes 101 and 102 before the application of the voltage is high is assumed to be a state in which data “0” is stored, and conversely, a state in which a diffusion of a metal ion toward the facing electrode by the application of the voltage results in a low resistance between the two electrodes 101 and 102 is assumed to be a state in which data “1” is stored, an operation of changing the element from the high resistance state to the low resistance state is referred to as a writing operation, and an operation of restoring the element from the low resistance state to the high resistance state is referred to as an erasure operation.