Patent ID: 7715220

Claim:
A memory apparatus comprising: a storage element configured to store and retain information based on a state of an electric resistance; and a circuit element connected in series to the storage element as a load, wherein when writing is defined as an operation in which a state of the storage element having a high resistance value is changed into a state of the storage element having a low resistance value, and when erasing is defined as an operation in which a state of the storage element having a low resistance value is changed into a state of the storage element having a high resistance value, a resistance value obtained from the written storage element is set to one of a plurality of different levels by controlling a voltage or a current applied to the circuit element or the storage element upon the writing, wherein the storage element includes a plurality of levels having low resistance values and a plurality of levels having high resistance values obtained after erasing, to each of which different information is allocated, one of the respective storage elements of the memory cells may store information having a ternary value or more, wherein, when the information is erased from the plurality of levels having low resistance values excluding the level having the lowest resistance value, a level of the storage element is: (a) initially changed to the level having the lowest resistance value; and (b) subsequently changed to the level having a higher resistance value; and wherein at least one of the levels having a low resistance value excluding the level having the lowest resistance value constantly passes the level having the lowest resistance value so erase characteristics can be constant.