Referring temporarily to FIGS. 24A, 24B, and 25A-25C, FIG. 24A illustrates the concentration of the dopant (e.g., boron) in the source/drain region 82 of an embodiment FinFET device. The y-axis illustrates the dopant concentration, and x-axis illustrates the vertical distance (e.g., depth) from the top of the source/drain region 82. The location D1 corresponds to the depth of the bottom of the source/drain region 82. Locations along the x-axis and to the right side of D1 correspond to portions of the fin under the source/drain region 82. FIG. 24B illustrates the concentration of germanium in the source/drain region 82. Note that the germanium concentration illustrated in FIG. 24B is due to the germanium contained in the material (e.g., SiGe) of the source/drain region 82, and is not the germanium concentration in the channel region of the fin. As illustrated in FIG. 24A, the dopant (e.g., boron) concentration in the source/drain region 82 is non-uniform, which will cause a non-uniform concentration of diffused dopant (e.g., boron) in the channel region of the fin. The effect of the non-uniform diffused dopant (e.g., boron) concentration is balanced out by a non-uniform germanium concentration in the channel region, in some embodiments.
