A method for manufacturing a semiconductor device includes forming a first field-effect transistor (FET) on a substrate, the first FET comprising a first plurality of channel regions extending in a first direction, and stacking a second FET on the first FET, the second FET comprising a second plurality of channel regions extending in a second direction perpendicular to the first direction, wherein the first FET comprises a first gate region extending in the second direction across the first plurality of channel regions, and the second FET comprises a second gate region extending in the first direction across the second plurality of channel regions.