A nonvolatile memory element is formed by layering a lower electrode, a variable resistor and an upper electrode in sequence. The variable resistor is formed in which crystallinity and amorphism are mixed. Thus, the nonvolatile memory element is formed. More preferably, the variable resistor is a praseodymium-calcium-manganese oxide represented by a general formula, Pr.sub.1-xCa.sub.xMnO.sub.3, that has been formed at a film forming temperature from 350.degree. C. to 500.degree. C. Alternatively, the variable resistor is formed as a film at a film forming temperature that allows the variable resistor to become of an amorphous state or a state where crystallinity and amorphism are mixed and, then, is subjected to an annealing process at a temperature higher than the film forming temperature, in a temperature range where the variable resistor can maintain the state where crystallinity and amorphism are mixed.
A storage device includes a memory cell having a storage element having a characteristic of changing from a state of a high resistance value to a state of a low resistance value by being supplied with a voltage equal to or higher than a first threshold voltage, and changing from a state of a low resistance value to a state of a high resistance value by being supplied with a voltage equal to or higher than a second threshold voltage different in polarity from the first threshold voltage, and a circuit element connected in series with the storage element, wherein letting R be a resistance value of the storage element after writing, V be the second threshold voltage, and I be a current that can be passed through the storage element at a time of erasure, R.gtoreq.V/I.
