A method includes forming a first and a second gate stack to cover a first and a second middle portion of a first and a second semiconductor fin, respectively, and performing implantations to implant exposed portions of the first and the second semiconductor fins to form a first and a second n-type doped region, respectively. A portion of each of the first and the second middle portions is protected from the implantations. The first n-type doped region and the second n-type doped region have different gate proximities from edges of the first gate stack and the second stack, respectively. The first and the second n-type doped regions are etched using chlorine radicals to form a first and a second recess, respectively. An epitaxy is performed to re-grow a first semiconductor region and a second semiconductor region in the first recess and the second recess, respectively.