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An O-POS (oxygen-doped polysilicon) film, deposited directly on silicon, is oxidized locally to create an active gate area. The electrical properties for the active gate area are the same as conventional p- and n-channel MOS devices, but the field area has an extremely high threshold voltage for both p- and n-type silicon substrates. The electrical properties in metal/oxidized O-POS/silicon and metal/oxide/O-POS/silicon structures have been investigated while varying the O-POS film thickness, oxygen concentration, local oxidation time, and silicon substrate resistivity. According to these basic studies, it is proposed that the high density of trapping centers existing in O-POS film is responsible for the high field threshold voltage. A applications of this process technology, a silicon-gate CMOS integrated circuit, and a high voltage n-channel MOS device are discussed.
Date of Publication: Aug. 1978