Ion implantation is used to modify the chemical properties of portions of a material, such that the modified portions respond differently to a chemical etching operation than do the unmodified portions of the material. In a further aspect of the present invention, ion implants into a wafer are performed at different energies so as to form three-dimensional patterns of chemically modified material within the body of a wafer. In a still further aspect of the present invention, three-dimensional patterns of etched tunnels within a wafer are formed, and in some embodiments provide for reduced parasitic capacitance and/or reduced leakage currents for electronic circuits.