| 摘要 |
PURPOSE:To prevent the decrease of threshold voltage caused by electric field concentration, restrain the inverse narrow channel effect, and microminiaturize a memory cell by installing a diffusion region of the sme conductivity type as a channel region on both ends in the width direction of the channel region of an island type epitaxial semiconductor layer. CONSTITUTION:The concentration of a semiconductor substrate 21a is made high, and that of an epitaxial semiconductor layer 21b is made comparatively low; an island type epitaxial semiconductor 21b is formed by isolating a part between grooves 23 with an insulator layer 22. On the peripheral part of the island type epitaxial semiconductor layer 21b, a P<+> type diffusion region 35 is formed, and arranged on the peripheral part where the gate electrode 30 of an MOS transistor functioning as a word line and the island type epitaxial semiconductor layer 21b intersect each other. The P<+> type diffusion region 35 is arranged on the peripheral end of an insulator layer 22 in the width direction of a channel region 28 of the MOS transistor, thereby preventing the decrease of the threshold voltage of a gate oxide film 29 caused by the electric field concentration at the peripheral end. As a result, the increase of current at the peripheral end in the width direction of the channel region 28 caused by electric field concentration can be prevented. |
