Method for fabricating strained-silicon metal-oxide semiconductor transistors

[0021]Please refer to FIGS. 7-10. FIGS. 7-10 illustrate a method of utilizing selective epitaxial growth process for fabricating a strained-silicon metal-oxide semiconductor transistor according to the preferred embodiment of the present invention. As shown in FIG. 7, a semiconductor substrate 40, such as a silicon substrate is first provided. The semiconductor substrate 40 includes a gate structure 42 thereon, in which the gate structure 42 includes a gate dielectric 44 and a gate 46 disposed on the gate dielectric 44. An ion implantation process is performed thereafter to inject a p-type or n-type dopant of smaller concentration into the semiconductor substrate 40. The implantation process preferably forms a lightly doped drain 54 in the semiconductor substrate 40 surrounding the gate structure 42. An offset spacer 48 is formed on the sidewall of the gate structure 42 and a spacer 50 is formed around the offset spacer 48 thereafter. Preferably, the gate dielectric 44 is composed insu