US Patent 9793323 Phase change memory with high endurance

A plurality of memory cells in a cross-point array with improved endurance is disclosed. Each memory cell, disposed between first and second conductors, includes a switch in series with a pillar of phase change material. The pillar has a Te-rich material at one end proximal to the second conductor, and an Sb-rich material at the other end proximal to the first conductor, wherein the current direction is from the first conductor to the second conductor.