Zinc stannate films have been prepared by RF magnetron sputtering using a ZnO:SnO2-target with 33 at. % SnO2. The influence of total pressure and substrate temperature on the electrical film properties was studied, A minimum resistivity of 2.9 × 10-3 Ωcm could be achieved. All zinc stannate films exhibit amorphous structure independent of the deposition conditions. The stability in hydrogen plasma was investigated with XPS. Finally, the films were applied as buffer layer and back contact in amorphous and microcrystalline p-i-n solar cells.