A 3D semiconductor device, the device including: a first level including a first single crystal layer and first transistors, where the first transistors each include a single crystal channel; first metal layers interconnecting at least the first transistors; and a second level including a second single crystal layer and second transistors, where the second level overlays the first level, where the second transistors are horizontally oriented and include a gate dielectric, where the gate dielectric includes hafnium oxide, where the second level is bonded to the first level, and where the bonded includes oxide to oxide bonds.