| 摘要 |
PURPOSE:To contrive to prevent dependence character of the threshold voltage upon channel width, and to enhance the characteristic and reliability of the element by a method wherein second impurity ions to form a layer of reversely conductive type from a semiconductor substrate are implanted by the quantity smaller than the implanting quantity of first impurity ions. CONSTITUTION:An oxide film 12 and a silicon nitride film 13 are formed on the P type silicon substrate 11, an oxide film 15 is formed on the whole surface, and boron (the first impurities) ions are implanted. Owing to the difference of film thickness of the oxide film 15, boron ion implanted layers 17 are formed selectively at the part excluding the silicon nitride film 13 and the neighborhood of the edge parts thereof. The oxide film 15 is removed, and arsenic (the second impurities) ions are implanted to form the arsenic ion implanted layers 18. Because the arsenic ion implanting quantity is smaller than the implanting quantity of boron ions, inversion preventing layers generated by arsenic ion implantation are formed only at the neighborhood of the edge parts of the silicon nitride film 13, impurity concentration on the silicon substrate 11 presents the condition as shown in the figure, the narrow channel effect can be suppressed, and forms the highly reliable device. |
