A novel and useful modified semiconductor fabrication technique for realizing reliable semiconductor quantum structures. Quantum structures require a minimization of the parasitic capacitance of the control gate and the quantum well. The modified semiconductor process eliminates the fabrication of the metal, contact, and optionally the raised diffusion layers from the quantum wells, thereby resulting in much lower well and gate capacitances and therefore larger Coulomb blockade voltages. This allows easier implementation of the electronic control circuits in that they can have larger intrinsic noise and relaxed analog resolution. Several processes are disclosed including implementations of semiconductor quantum structures with tunneling through an oxide layer as well as tunneling through a local well depleted region. These techniques can be used in both planar semiconductor processes and 3D, e.g., FinFET, semiconductor processes. A dedicated process masking step is used for realizing the raised diffusions. In addition, the edge of the raised diffusion layer may be placed either in the gate region or the active layer region.