| 摘要 |
PURPOSE:To form the high-reliability ICs on the same Si substrate by arranging a high concentration PSG in a low breakdown voltage element region so as to level the surface and arranging a low concentration PSG in a high breakdown voltage element region so as to prevent moisture absorption. CONSTITUTION:After a gate electrode 20 of a low breakdown voltage PMOSFET, a gate electrode 21 of the same NMOSFET, a gate electrode 22 of a high breakdown voltage are formed by P-doped polysilicon as predetermined, an insulating film 55 is formed in the periphery by thermal oxidation. The substrate is covered with an Si3N4 layer 56 and the Si3N4 except in the high breakdown voltage element region (Hb) is removed. The high concentration PSG57 is deposited followed by a heat treatment to level the surface of substrate. Openings 58 are formed in the low breakdown voltage element region (Lb) and the PSG57 and Si3N4 56 on the high breakdown voltage region are removed. Then the substrate is covered with the low concentration PSG59 and openings 60 are formed and Al wiring 61 is arranged. By this constitution, disconnection of wiring does not occur and because the high breakdown voltage element region is covered with the low concentration PSG, polarization effect or a bad influence due to moisture absorption on the characteristics can be eliminated thereby improving the reliability. |
