Forming method of performing forming on variable resistance nonvolatile memory element, and variable resistance nonvolatile memory device

Abstract

In forming, an automatic forming circuit () included in a nonvolatile memory device () causes a constant current IL to flow in a selected memory cell having a considerably high initial resistance. When the forming generates a filament path in the memory cell and thereby a resistance value is decreased, a potential of a node NBL and a potential of a node Nin are also decreased. If the potentials become lower than that of a reference voltage Vref, an output NO of a difference amplifier () for detecting forming success is activated, and a forming success signal Vfp is activated after a delay time depending on the number n of flip flops FFto FFn and a clock signal CLK. Thereby, a switch transistor () is in a non-conducting state and the forming on a variable resistance element is automatically terminated.