US Patent 7605410 Semiconductor device and manufacturing method thereof

The invention provides a novel memory for which process technology is relatively simple and which can store multivalued information by a small number of elements. A part of a shape of the first electrode in the first storage element is made different from a shape of the first electrode in the second storage element, and thereby voltage values which change electric resistance between the first electrode and the second electrode are varied, so that one memory cell stores multivalued information over one bit. By partially processing the first electrode, storage capacity per unit area can be increased.