| 摘要 |
PURPOSE:To obtain a gate insulating film forming method of an MOS type semiconductor device having less variation in a threshold voltage by forming a silicon oxidized film having a specific thickness or larger and then removing it to the specific thickness or smaller. CONSTITUTION:After an element region 11 is formed on a sapphire 10, hydrogen combustion oxidation is performed. Then, an SiO2 film 12 having 400Angstrom or thicker is grown. Then, when this is etched in 1%-HF aqueous solution for 3min., a silicon oxidized film 13 having 300Angstrom or thinner is obtained. After a VT control is performed by implanting an impurity, a gate electrode 14 is formed. Then, an MOS device which is strong against radiation can be formed. This can also be applied to a silicon wafer. Wet oxidation or dry oxidation at approx. 1,000 deg.C may be used instead of the hydrogen combustion oxidation. The concentration of HF aqueous solution may be any %, and may also be capable of etching SiO2 as fluorided ammonium aqueous solution. When radiation is emitted to the MOS type transistor, positive charge is collected at the gate insulating film, with the result that the threshold voltage VT of the transistor is shifted to negative side together with PMOS and NMOS. |
