The present invention provides a method for forming multiple gate oxide layers with different thickness in one chip by using a simple process. Embodiments include adding dummy structures, formed simultaneously with the gate electrodes, to \u201cfill in\u201d the spaces between isolated gate electrodes, such that the spacing between the gate electrodes and the dummy structures is the same as the spacing between the densest array of device structures on the substrate surface. A waveform shaping section, when an amplitude of the second modulated signal is larger than a regulated value generates a waveform-shaped modulated signal.