element iupac form antimony sb and tellurium te a compound layer of a chalcogen antimony sb and tellurium te a compound layer of a group va element iupac form antimony sb and selenium se and or a compound layer of a chalcogen with the exception of selenium se antimony sb and selenium se in one embodiment u201c chalcogenide u201d pcm 39 s comprise for example ge 2 sb 2 te 5 sbte and in 2 se 3 the so called ge u2014 sb u2014 te gst materials however are the pcm 39 s of choice for optical memory devices they are also the leading candidates for a new generation of non volatile electronic memory via 12 and spacer 18 extend toward and terminate at electrode 20 which may comprise at least one of titanium ti titanium nitride tin tantalum nitride tan molybdenum nitride mon niobium nitride nbn titanium silicon nitride tisin titanium aluminum nitride tialn titanium boron nitride tibn zirconium silicon nitride zrsin tungsten w tungsten nitride wn graphite carbon nitride cn tungsten silicon nitride wsin tungsten boron nitride wbn zirconium aluminum nitride zraln molybdenum silicon nitride mosin molybdenum aluminum nitride moaln tantalum silicon nitride tasin tantalum aluminum nitride taaln titanium oxynitride tion titanium aluminum oxynitride tialon tungsten oxynitride won and tantalum oxynitride taon electrode 20 may be formed by a deposition process such as a physical vapor deposition pvd method a cvd method or an ald.