Hydrothermal processes can produce regular micro-/nano-structures easily; but their placement or position is difficult to control, and the obtainable structures tend to be random. For controlling the crystal growth, two types of definite and regular structures were obtained. The first ones were ZnO urchin-like structures synthesized from located ZnO particles as the nuclei. These structures were found to work as gas sensors utilizing a wide surface area. The second one was a vertically aligned TiO2 nanorod array synthesized on a fluorine-doped tin oxide substrate that has a similar lattice constant to rutile TiO2. Super-hydrophobicity after ultraviolet irradiation was then examined. Finally, the synthesized TiO2 array was peeled off and transferred onto a resin sheet. We determined that the substrate could be subjected to repeated hydrothermal synthesis, thereby demonstrating the reusability of the substrate. These results demonstrate the applicability of these processes for industrial applications.