Semiconductor structures and methods of fabrication are provided, with one or both of an extended source-to-channel interface or an extended drain-to-channel interface. The fabrication method includes, for instance, recessing a semiconductor material to form a cavity adjacent to a channel region of a semiconductor structure being fabricated, the recessing forming a first cavity surface and a second cavity surface within the cavity; and implanting one or more dopants into the semiconductor material through the first cavity surface to define an implanted region within the semiconductor material, and form an extended channel interface, the extended channel interface including, in part, an interface of the implanted region within the semiconductor material to the channel region of the semiconductor structure. In one embodiment, the semiconductor structure with the extended channel interface is a FinFET.