Undoped SnO2-x thin films with amorphous phase were prepared at room temperature by radio frequency magnetron sputtering, and the changes in electrical, optical and structural properties were investigated upon annealing in atmosphere. The amorphous SnO2-x film had the minimum resistivity of 1.5 x 10(-3) Omega cm and the highest Hall mobility of 22 cm(2)/V s, which were comparable to those observed in polycrystalline doped SnO2 films. Examination of the temperature dependent Hall mobility revealed the grain boundary scattering as the dominant scattering mechanism for the crystallized SnO2-x films. Analysis made by using four coefficients instrument showed that undoped SnO2-x films had the characteristics of degenerate semiconductor with non-parabolic band structure, and that ionized impurity scattering with free electron screening was dominant mobility limiting mechanism in amorphous SnO2-x films. (c) 2006 Published by Elsevier B.V.