| 摘要 |
PURPOSE:To mitigate the concentration of stress and to prevent the variation in characteristics due to piezoelectric polarization, by forming a gate electrode and an insulation coating film of respective materials that exert equivalent stresses on a semiconductor substrate, and covering the gate electrode and the vicinity thereof with the coating film having a flat surface. CONSTITUTION:An N type channel layer 2, a gate electrode 3 and N<+> type source and drain regions 4 are provided on a semiinsulating GaAs substrate 1, and an SiNXOY film 5 is adhered over there. The values of X and Y are selected such that the stress it exerts on the substrate 1 is equivalent to the stress The the gate electrode exerts on the substrate 1 if they have the same thickness (e.g. when the electrode 3 is W5Si3, X=0.6 and Y=1.5). Subsequently, a resist film 6 is provided flatly, and then etching is performed so as to flatten the surface of the SiNXOY film. Source and drain electrodes 7 are formed there after. Accordingly, the stress concentrated to the vicinity of the gate electrode of an FET is decreased and therefore no piezoelectric polarization occurs. Thus, the variation in the gate threshold voltage can be eliminated. |
