Stacked gate-all-around finfet and method forming the same

A device includes a first semiconductor strip, a first gate dielectric encircling the first semiconductor strip, a second semiconductor strip overlapping the first semiconductor strip, and a second gate dielectric encircling the second semiconductor strip. The first gate dielectric contacts the first gate dielectric. A gate electrode has a portion over the second semiconductor strip, and additional portions on opposite sides of the first and the second semiconductor strips and the first and the second gate dielectrics.