Patent ID: 8325508

Claim:
A method of writing to a variable resistance nonvolatile memory element that reversibly changes between a high resistance state and a low resistance state depending on a polarity of an applied voltage pulse, wherein the variable resistance nonvolatile memory element has characteristics of (i) changing from the low resistance state to the high resistance state due to application of a voltage having an absolute value equal to or greater than an absolute value of a first voltage, (ii) changing to the high resistance state having a maximum resistance value due to application of a second voltage having an absolute value greater than the absolute value of the first voltage, and (iii) changing to the high resistance state having a resistance value lower than the maximum resistance value due to application of a third voltage having an absolute value greater than the absolute value of the second voltage, and each of the first, second, and third voltages has a first polarity, said writing method comprising: a high resistance writing step of changing the variable resistance nonvolatile memory element from the low resistance state to the high resistance state, by applying a voltage pulse having the first polarity to the variable resistance nonvolatile memory element; and a low resistance writing step of changing the variable resistance nonvolatile memory element from the high resistance state to the low resistance state, by applying a voltage pulse having a second polarity to the variable resistance nonvolatile memory element, wherein the voltage pulse applied in said high resistance writing step has an absolute value which is equal to or greater than the absolute value of the first voltage and equal to or smaller than the absolute value of the second voltage.