FIGS. 18A to 18C are explanatory diagrams showing a sensor device in accordance with still another embodiment of the present invention, in which FIG. 18A is a plan view of the sensor device, FIG. 18B is a cross-sectional view of the sensor device taken along a line VIII--VIII, and FIG. 18C is a cross-sectional view of the sensor device taken along a line VII--VII;