A 3D semiconductor device, the device including: a first single crystal layer including a plurality of first transistors and a first metal layer, where the first metal layer includes interconnecting the first transistors forming a plurality of logic gates; a plurality of second transistors overlaying the first single crystal layer; a plurality of third transistors overlaying the second transistors; a second metal layer overlaying the third transistors; and Input/Output pads to provide connection to external devices, where the third transistors are aligned to the first transistors with less than 40 nm misalignment, where the first single crystal layer includes an Electrostatic Discharge (“ESD”) structure connected to at least one of the Input/Output pads, where at least one of the third transistors is a junction-less transistor, and where a memory cell includes at least one of the third transistors.