We are reporting here on the inexpensive fabrication of large three-dimensional and highly oriented porous microrod array of n-type ZnO semiconductor with a unique designed architecture consisting of well-defined, length-tailored, monodisperse, perpendicularly oriented single-crystalline hexagonal rods, grown directly onto polycrystalline, single-crystalline, or amorphous substrates, from an aqueous solution of zinc salt at low temperature.