Abstract: A semiconductor device includes a substrate, a device isolation layer at the substrate and defining an active region, and a gate electrode on the substrate and extending across the active region. The active region includes a first active region and a second active region, and the first and second active regions are arranged at opposing sides of a centerline of the gate electrode. At least one of the first and second active regions has a width decreasing from a region outside the gate electrode toward the centerline of the gate electrode, and the first and second active regions are asymmetric with respect to the centerline of the gate electrode.