| 摘要 |
PURPOSE:To ensure a prolonged service life for memory by a method wherein a floating gate type semiconductor memory is provided in an n type Si substrate p well and an erase electrode is provided in a p<+> layer in the well. CONSTITUTION:The SiO2 layer 12 laid on an n type Si substrate 11 is provided with p well covered with an Si3N4 mask and B<+> ion implantation is accomplished for a channel stop feature. Oxidation follows for the formation of a field oxide film 12 and a part thereof is removed for the creation of a 100Angstrom thick SiO2 film 12''. Next, a doped polycrystalline Si film 16 is laid for the creation of an oxide film 17, which is further covered with a doped polycrystalline Si film 18 wherewith a floating gate 16 and a controlling gate 18 are produced with help of a resist mask. The product is covered with an SiO2 film 19, polycrystalline line Si films 20 and 20'' are provided, a p well is ion implanted with the layer 20 as a mask for the creation of an n<+> layer, a p<+> layer is selectively formed, and terminals for an erase line E, a word line W, a bit line B, and wirings for a CMOS are provided. In this construction, zero voltage V is applied to the terminal W at the time of read. Positive voltage here being 5V at the maximum thanks to the insulator film 12'' being extremely thin, information stored remains free of erasure for a prolonged period of time. |
