Nanostructured semiconductor and functionalized dielectric layers demonstrate high-absorbance which is extremely important for the development of new generation solar cells. We demonstrate that nanostructuring of semiconductor materials significantly increases their radiation hardness, a very important issue for space applications. Nanostructured semiconductor and dielectric templates represent an important basis for the production of novel nanocomposites, including smart and negative-refractive index materials for optoelectronic and photonic applications. We demonstrate that electrochemistry is one of the most efficient and cost-effective approach for controlling the architecture of III-V and II-VI semiconductor compounds on the nanometer scale by introducing porosity. A variety of architectures are demonstrated, including periodic spatial distribution of pores achieved by anodic etching governed by self-organization phenomena. A neutral electrolyte based on aqueous solution of NaCl is proposed instead of commonly used aggressive acids or alkaline electrolytes for the purpose of producing nanostructured semiconductor films. This technology in combination with electrochemical deposition of nanowire, nanodot, and nanotubular metallic structures in semiconductor and dielectric nanotemplates possessing ordered two-dimensional hexagonal arrays of pores is increasingly used for the fabrication of metalo-dielectric nanocomposites for optoelectronic, photonic and plasmonic applications. Special attention is paid to the development of methods for the fabrication of nanostructured layers of wide-band gap compounds such as GaN, ZnO, and TiO₂. These methods include metalorganic chemical vapor deposition for growth of ZnO layers of various morphologies, photoelectrochemical treatment for nanostructuring GaN layers, and electrochemical oxidation of Ti foils for the fabrication of nanotubular TiO₂ structures. A new technology, the so-called "surface charge lithography", for micro- and nanofabrication based on GaN layers is presented. Applications of nanostructured ZnO layers in micro- and nano-lasers, GaN layers in electronic sensors, and TiO2 layers in photonic crystals are demonstrated.