Different from the common method used for improving the conductivity of ZnO through doping and/or heat treatments, we have used an alternative, i.e., through the introduction of an Al mid-layer without any heat treatment, to enhance the electrical conductivity. We have investigated a nano-scaled sandwich structure consisting of two outer layers of ZnO and a mid-layer of an ultra-thin aluminum thin film for the improvement of the electrical conductivity of ZnO. The nano-scaled ZnO/Al/ZnO thin films were obtained using an RF sputter deposition method. A number of different RF sputter deposition pressures were used to deposit the ZnO layers with thicknesses ranging from 5 to 180 nm. Al layers with various thicknesses ranging from less than 30 to 210 angstrom were also obtained using the same RF sputter deposition system. The optical transmittance and electrical resistivity of ZnO films, Al films, and ZnO/Al/ZnO thin films were investigated and compared. We have shown that the use of an ultra-thin Al mid-layer enhances the electrical conductivity of ZnO without scarifying its optical transmittance. Furthermore, the electrical transport in ZnO/Al/ZnO films is believed to be dominated by the electrons in the Al but not by the carrier concentration in the ZnO.