| 摘要 |
PURPOSE:To prevent a movable ion from being invaded from a contact hole and to enhance reliability by a method wherein a nonvolatile memory cell is covered with a silicon nitride film and the circumference of a wiring contact hole to a semiconductor substrate constituting the above memory cell is surrounded by the silicon nitride film. CONSTITUTION:After an etching operation of a two-layer polysilicon structure is finished and ions used to form a source-drain 104 are implanted, a thick thermal oxide film 105 is formed on the source-drain N<+> diffusion layer 104 by accelerated oxidation. The thermal oxide film 105 is removed by an etching- back operation; an Si3N4 film 106 with about 200Angstrom is deposited by an LPCVD method. Then, a PSG layer 107 to be used as an interlayer film is deposited on it; after that, a contact hole 109 is made; a metal wiring layer 108 is formed; an EPROM cell is completed. Because the upper part of a memory cell and the circumference of the contact hole are covered with the Si3N4 film 106, movable ions cannot reach the memory cell part from the contact hole 109. |
