US Patent 7575958 Programmable fuse with silicon germanium

A programmable fuse and method of formation utilizing a layer of silicon germanium (SiGe) (e.g. monocrystalline) as a thermal insulator to contain heat generated during programming. The programmable fuse, in some examples, may be devoid of any dielectric materials between a conductive layer and a substrate. In one example, the conductive layer serves as programmable material, that in a low impedance state, electrically couples conductive structures. A programming current is applied to the programmable material to modify the programmable material to place the fuse in a high impedance state.