A dynamic quantity sensor includes a semiconductor substrate, a movable electrode, first fixed electrodes and second fixed electrodes. When a watermark part of the banknote 21 is measured by the line light sensor 23, a watermark pattern is detected by a light transmissive sensor, and that pattern is not detected by a light reflective sensor, the banknote 21 is determined to be a true banknote. The semiconductor body further includes an IGBT-cell with a body region forming a first pn-junction with the base region, and a diode-cell with an anode region forming a second pn-junction with the base region.