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