US Patent 7254059 Multilevel phase-change memory element and operating method

A multilevel phase change memory element and operating method and electrodes, which are configured in a parallel structure to form a memory cell. A voltage-drive mode is employed to control and drive the memory element such that multilevel memory states may be achieved by imposing different voltage levels. The provided multilevel phase-change memory element has more bits and higher capacity than that of a memory element with a single phase-change layer.