A semiconductor gas sensor based on WO3 doped TiO2 having a rutile phase was fabricated on an Al2O3 substrate. The sensing film of the sensor was deposited by using screen printing. In order to enhance the sensitivity of the sensor, the sensing film was fabricated with a porous shape by high temperature heat treatment and the TiO2 layer was doped with WO3 to improve the gas selectivity. The surface topography and inner morphological properties of the sensing film were characterized with scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray diffraction (XRD). The gas sensing properties of the fabricated sensor were evaluated by detecting NO2 and other oxidizing gases (CO, O-2 and CO2) at high operating temperature (600 degrees C). (C) 2009 Elsevier B.V. All rights reserved.