US Patent 10910558 Memory device

A phase-change memory cell includes, in at least a first portion, a stack of at least one germanium layer covered by at least one layer made of a first alloy of germanium, antimony, and tellurium. In a programmed state, resulting from heating a portion of the stack to a sufficient temperature, portions of layers of germanium and of the first alloy form a second alloy made up of germanium, antimony, and tellurium, where the second alloy has a higher germanium concentration than the first alloy.