US Patent 7423300 Single-mask phase change memory element

A memory device. An array of memory elements is formed on a semiconductor chip. A parallel array of word lines extends in a first direction, connecting each memory element to a data source, and a parallel array of bit lines extends in a second direction, connecting each memory element to a data source, the second direction forming an acute angle to the first direction. The connection between each bit line and each memory element is a phase change element composed of memory material having at least two solid phases.