In this work, the n-type FET chips were fabricated by Toppan Co.,Ltd. (Japan). Each FET chip consist of two gate electrodes in which the gate oxide surface is SiO2 layer on the Si substrate with a size of 1000 m in width and 10 m in length. All electrical measurements were performed using a digital source meter (Keithley 2612). X-ray photoelectron spectroscopy (XPS) analysis was carried out for the specimens prepared not on FET chip but on Si wafer with SiO2 layer using a micro XPS instrument (PHI-5000 Versa Probe WS, ULVAC-PHI Inc.) with monochromatic Al K X-ray source.