| 摘要 |
PURPOSE:To easily change the direction of voltage between the floating electrode and impurity diffusion layer by providing, on the semiconductor substrate, the floating electrode and the capacitance variable electrode for charging and discharging of the semiconductor variable capacitance element having the floating electrode of which external part is insulated. CONSTITUTION:The P<-> type diffusion layer 2 exists within the N<-> type semiconductor substrate 1. The P<+> type diffusion layer 3 for the contact with power source exists within the P<-> type diffusion layer 2. The floating electrode 5 which is covered with the oxide insulation film 4 and is insulated from the external circuit exists on the layer 2 and the capacitance electrode 6 exists on the electrode 5 through the film 4. The P<-> type diffusion layer 7 for insulating isolation exists in the substrate 1 and the capacitance variable electrode N<+> type diffusion layer 8 exists in the layer 7. The insulated oxide film 9 located between the layer 8 and electrode 5 is thin in order to form a low capacitance variable electrode. When the layer 8 is biased positive for the layer 2, a capacitance value is reduced, or when biased negative, capacitance value is increased. |
