| 摘要 |
PURPOSE:To form a double well of self-alignment and thus contrive to increase the integration degree and the yield by a method wherein the thin forth insulation film is formed on the surface of a semiconductor substrate after removing the first, second, and third insulation films, and the first and second impurity layers are pressed in to the degree of almost contact by heat treatment. CONSTITUTION:A thermal oxide film 2 is formed on an N type semiconductor substrate 1, and thereafter an N type impurity layer 6 of a higher concentration than that of the substrate is formed by ion implantation. An oxide film 7 and a nitride film 8 are adhered on the thermal oxide film 2, the nitride film 8 is patterned with a photo resist 3 as a protection film, afterwards the photo resist 3 is removed, and the oxide film 7 and the thermal oxide film 2, and the N type impurity layer 6 is etched with the patterned nitride film 8 as a protection film. A P type impurity layer 4 is formed by ion implantation with the nitride film 8 as a blocking film, finally a thermal oxide film 9 is formed over the entire surface after removing the nitride film 8, the oxide film 7, and the thermal oxide film 2, heat treatment is performed, and accordingly the double well is formed by pressing in to the degree that the N type impurity layer 6 almost contacts the P type impurity layer 4. |
