1. A non-volatile memory device, comprising: a bottom electrode; a first layer of an undoped phase change material having a first thickness, a first melting temperature and a first glass transition temperature, disposed above and electrically coupled to the bottom electrode; a second layer of a phase change material having a first doping level, a second thickness, a second melting temperature and a second glass transition temperature, disposed above and electrically coupled with the first layer; a third layer of an undoped phase change material having a third thickness, a third melting temperature and a third glass transition temperature, disposed above and electrically coupled with the second layer; a fourth layer of a phase change material having a second doping level, a fourth thickness, a fourth melting temperature and a fourth glass transition temperature, disposed above and electrically coupled with the third layer; and a top electrode disposed above and electrically coupled with the fourth layer.