US Patent 7994015 NMOS transistor devices and methods for fabricating same

NMOS transistors having controlled channel strain and junction resistance and methods for the fabrication of same are provided herein. In some embodiments, a method for forming an NMOS transistor may include providing a substrate having a p-type silicon region and a gate stack disposed thereon, the gate stack partially defining a source and a drain region; depositing an undoped first silicon layer having a lattice adjusting element atop the p-type silicon region and within the source and the drain regions; and depositing a second silicon layer having a lattice adjusting element and an n-type dopant atop the undoped first silicon layer.