Variable resistance nonvolatile memory element writing method and variable resistance nonvolatile memory device

A variable resistance nonvolatile memory device comprising:

• a memory cell including a variable resistance nonvolatile memory element;
• and
• a write control unit configured to, by applying a voltage pulse to the memory cell, perform writing for reversibly changing the variable resistance nonvolatile memory element between a first resistance state and a second resistance state according to a polarity of the applied voltage pulse,
• wherein the variable resistance nonvolatile memory element includes a first electrode, a second electrode, and a variable resistance layer placed between the first electrode and the second electrode,
• the variable resistance layer includes an oxygen-deficient first transition metal oxide layer that is in contact with the first electrode, and a second transition metal oxide layer that is in contact with the second electrode and is lower in oxygen deficiency than the first transition metal oxide layer,
• the variable resistance nonvolatile memory element has characteristics of changing to the first resistance state when, with respect to one of the first electrode and the second electrode, a first voltage pulse having a positive potential and equal to or more than a first threshold voltage is applied to an other one of the first electrode and the second electrode, and changing to the second resistance state when, with respect to the other one of the first electrode and the second electrode, a second voltage pulse having a positive potential and equal to or more than a second threshold voltage is applied to the one of the first electrode and the second electrode, and
• the write control unit is configured to, during a writing operation, successively apply a first voltage pulse set and a memory cell value measurement a plurality of times, the first voltage pulse set including a first preliminary voltage pulse and the first voltage pulse, wherein in the first voltage pulse set, the first voltage pulse is applied to the variable resistance nonvolatile memory element subsequent to the first preliminary voltage pulse when changing the variable resistance nonvolatile memory element from the second resistance state to the first resistance state, such that a value of the memory cell changes in accordance with each successive application of the first voltage pulse set, the first preliminary voltage pulse being smaller in voltage absolute value than the second threshold voltage and different in polarity from the first voltage pulse.