Abstract: Doping techniques for fin-like field effect transistors (FinFETs) are disclosed herein. An exemplary method includes forming a fin structure, forming a doped amorphous layer over a portion of the fin structure, and performing a knock-on implantation process to drive a dopant from the doped amorphous layer into the portion of the fin structure, thereby forming a doped feature. The doped amorphous layer includes a non-crystalline form of a material. In some implementations, the knock-on implantation process crystallizes at least a portion of the doped amorphous layer, such that the portion of the doped amorphous layer becomes a part of the fin structure. In some implementations, the doped amorphous layer includes amorphous silicon, and the knock-on implantation process crystallizes a portion of the doped amorphous silicon layer.

Abstract: A method includes etching a first semiconductor fin and a second semiconductor fin to form first recesses. The first and the second semiconductor fins have a first distance. A third semiconductor fin and a fourth semiconductor fin are etched to form second recesses. The third and the fourth semiconductor fins have a second distance equal to or smaller than the first distance. An epitaxy is performed to simultaneously grow first epitaxy semiconductor regions from the first recesses and second epitaxy semiconductor regions from the second recesses. The first epitaxy semiconductor regions are merged with each other, and the second epitaxy semiconductor regions are separated from each other.