A thermal type air flow rate sensor is formed with at least a heating resistor and a temperature measuring resistor on a semiconductor substrate via an electric insulation film, by forming the heating resistor and the temperature measuring resistor with an impurity doped silicon (Si) semiconductor thin film, and by performing high concentration doping process so that an electric resistivity (&rgr;) of the silicon (Si) semiconductor thin film is less than or equal to 8×10−4 &OHgr; cm, with simplified fabrication process for formation of the silicon (Si) semiconductor thin film at the same impurity concentration simultaneously in a lump at low cost.