US Patent 7649226 Source and drain structures and manufacturing methods

A semiconductor structure includes a semiconductor substrate; a first gate dielectric on the semiconductor substrate; a first gate electrode over the first gate dielectric; a first lightly doped source or drain (LDD) region in the semiconductor substrate and adjacent the first gate dielectric, wherein the first LDD region comprises arsenic; and a first deep source/drain region in the semiconductor substrate and adjacent the first gate dielectric. The first deep source/drain region comprises phosphorous, and a first phosphorous junction depth in the first deep source/drain region is greater than about three times a first arsenic junction depth in the first deep source/drain region.