A gate structure includes a gate and a first isolation structure having a top surface and a bottom surface. The gate includes a first sidewall adjacent to the first isolation structure, a second sidewall, a first horizontal surface adjacent to a bottom edge of the first sidewall and a bottom edge of the second sidewall, the first horizontal surface being between the top surface of the first isolation structure and the bottom surface of the first isolation structure. The gate also includes a second horizontal surface adjacent to a top edge of the second sidewall. An effective channel width defined by the gate structure includes a height of the second sidewall and a width of the second horizontal surface.