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; and a second level including a second single crystal layer, the second level including second transistors, where a top surface of the first level includes a first oxide region and a bottom surface of the second level includes a second oxide region, where the second level overlays the first level, where the second level is bonded to the first level, where the bonded includes oxide to oxide bonds, and where the second transistors are raised source drain extension transistors.