| 摘要 |
PURPOSE:To prevent excavation at stepped locations in the fabrication of a first and second gate for a FAMOS device by a method wherein a first polycrystalline Si layer is deposited, etched into a first gate, whose exposed surface is then converted into an SiO2 film and the entire surface including them is covered with a deposited second polycrystalline Si layer, which is etched into a second gate with an Si3N4 film acting as a mask, and the rest is converted into an SiO2 film. CONSTITUTION:Thick field oxide films 202 are provided along the periphery of an Si substrate 201 and a thin gate oxide film is laid down between the field oxide films 202. The gate oxide film is then covered with a first polycrystalline Si layer which is in turn photoetched into a floating gate 204. The gate 204 acts as a mask in a process wherein a source and drain region 208 is diffusedly formed within the substrate 201. Heat treatment follows for the creation of an SiO2 film 205 on the exposed surface of the gate 204. After this, the entire surface is covered with a second polycrystalline Si layer 206 whereon an Si3N4 film 207 is provided at a place corresponding to the gate 204, to be etched into a controlling gate 210, which is followed by a process to convert into an SiO2 film 209 the layer 206 surrounding the gate 210. |
