Transparent and highly conducting amorphous and crystalline Al doped ZnO thin films were grown on glass substrate at room temperature by RF magnetron sputtering. The structural, electrical, morphological and optical properties of amorphous and crystalline Al doped ZnO thin films were studied. The XRD pattern revealed that the crystalline film corresponds to hexagonal wurtzite structure with (002) preferred orientation. The minimum resistivity 4.2 x 10-3 ?m was observed for crystalline film. The AFM and transmission spectra show that the average roughness of the crystalline film is higher than that of the amorphous film. Photoluminescence spectrum shows band to band transition in UV region and defect related transitions peaks in visible region. The deposited crystalline film shows low optical bandgap, 3.32 eV than amorphous film, 3.51 eV.