A method for manufacturing a semiconductor device including an upper-channel implant transistor is provided. The method includes forming one or more fins extending in a first direction over a substrate. The one or more fins include a first region along the first direction and second regions on both sides of the first region along the first direction. A dopant is shallowly implanted in an upper portion of the first region of the fins but not in the second regions and not in a lower portion of the first region of the fins. A gate structure extending in a second direction perpendicular to the first direction is formed overlying the first region of the fins, and source/drains are formed overlying the second regions of the fins, thereby forming an upper-channel implant transistor.