Buried source and drain (BSD) structure for ultra-shallow junction using selective deposition of highly doped amorphous silicon

A buried source and drain (BSD) structure, that realizes ultra-shallow junctions, is proposed. Regions for source and drain are etched off. An in-situ highly doped amorphous silicon layer is selectively deposited on the etched region and is crystallized by solid phase epitaxy. Junction depth can be reduced to 10 nm without lowering the dopant concentration, because the doped layer can be used as source and drain. Thus, the sheet-resistance was lowered to 300 /spl Omega// for a junction with the depth of 30 nm. Junction leakage current for the BSD structure was equal to or lower than that fabricated by ion-implantation.