3D vertically-integrated FETs electrically coupled by integrated vertical FET-to-FET interconnects for reducing an area of CMOS cell circuits are disclosed. Vertically integrated FETs reduce a footprint area of an integrated circuit chip. The FETs include horizontal channel structures that are vertically integrated by stacking a second channel structure of a second FET above a first channel structure of a first FET. The first and second FETs can include a combination of a PFET and NFET that can be used to form a 3D CMOS cell circuit as an example. The area occupied by the 3D CMOS cell circuit includes interconnects for electrically coupling terminal regions of the FETs internally and externally. Vertical FET-to-FET interconnects extend between the FETs to electrically couple terminal regions of the FETs to reduce a number of vias from a semiconductor layer of the 3D CMOS cell circuit to metal interconnect layers above the vertically-integrated FETs.