A memory cell signal window testing apparatus 101 and method for testing the signal window of a memory are disclosed. An integer number of sectors, are provided in each physical track. The light source is configured to irradiate light on the annular slit. With this arrangement, a semiconductor device having a capacitive element for use in a charge pump circuit or the like has its chip area prevented from being increased, allow the capacitive element to have a highly accurate capacitance, and can be manufactured in a reduced number of fabrication steps.