A semiconductor device includes a dielectric dummy gate, a plurality of first semiconductor fins, and a plurality of second semiconductor fins. The dielectric dummy gate extends along a first direction. The first semiconductor fins extend along a second direction within a first core circuit region on a first side of the dielectric dummy gate, and the second direction is substantially perpendicular to the first direction. The second semiconductor fins extend along the second direction within a second core circuit region on a second side of the dielectric dummy gate opposite the first side of the dielectric dummy gate. A number of the second semiconductor fins within the second core circuit region is less than a number of the first semiconductor fins within the first core circuit region, and each of the second semiconductor fins has a width less than a width of each of the first semiconductor fins.