A conductive strap spacer is formed within a buried strap cavity above an inner electrode recessed below a top surface of a buried insulator layer of a semiconductor-on-insulator (SOI) substrate. A portion of the conductive strap spacer is metallized by reacting with a metal to form a strap metal semiconductor alloy region, which is contiguous over the conductive strap spacer and a source region, and may extend to a top surface of the buried insulator layer along a substantially vertical sidewall of the conductive strap spacer. The conductive strap spacer and the strap metal semiconductor alloy region provide a stable electrical connection between the inner electrode of the deep trench capacitor and the source region of the access transistor.