Semiconductor devices and methods of forming the same are provided. A semiconductor device includes a substrate having a fin. A first nanowire is disposed on the fin and a second nanowire is disposed on the fin, the second nanowire being laterally separated from the first nanowire. A gate structure extends around the first nanowire and the second nanowire. The gate structure also extends over a top surface of the fin. The first nanowire, the second nanowire, and the fin form a channel of a transistor.