This invention provides structures and a fabrication process for incorporating thin film transistors in back end of the line (BEOL) interconnect structures. The structures and fabrication processes described are compatible with processing requirements for the BEOL interconnect structures. The structures and fabrication processes utilize existing processing steps and materials already incorporated in interconnect wiring levels in order to reduce added cost associated with incorporating thin film transistors in the these levels. The structures enable vertical (3D) integration of multiple levels with improved manufacturability and reliability as compared to prior art methods of 3D integration.