A 3D semiconductor device, the device including: a first level including a first single crystal layer, the first level including first transistors, where each of the first transistors includes a single crystal channel; first metal layers interconnecting at least the first transistors; a second metal layer overlaying the first metal layers; 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 at least one of the second transistors includes a transistor channel, where the at least one of the second transistors transistor channel includes non-silicon atoms, where the second level is directly bonded to the first level, and where the bonded includes direct oxide-to-oxide bonds.