| 摘要 |
It is an object of the present invention to provide a semiconductor memory device and a method of manufacturing thereof capable of increasing the integration thereof and having a high operation reliability. Anisotropic etching having a high selectivity to silicon oxide (SAS etching) is carried out by using a resist layer 56, a stacked gate 46, a thermal oxidation layer 58 as a mask. A field oxidation layer 44 located between low density sources LS is selectively removed by carrying out the SAS etching. A width w3 of the field oxidation layer 44 thus removed is not much less than a width w2 between the stacked gates 46 located adjacently because the thermal oxidation layer 58 formed on sides of the stacked gate 46 is thin in its thickness. A diffusion source wiring 55 formed by carrying out subsequent processes such as ion implantation and thermal diffusion can be formed in an appropriate width. A gate edge 59 of the stacked gate 46 can fully be protected with the thermal oxidation layer 58 even in the SAS etching while the thermal oxidation layer 58 is etched in its height during the SAS etching.
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