| 摘要 |
PURPOSE:To improve reliability, and to reduce the area of a pattern by increasing impurity concentration in a drain region in a thin-film gate oxide film transistor with a floating gate and lowering impurity concentration in a region being in contact with the gate in a source region. CONSTITUTION:A source region 23, an N<+> type drain region 24, an N<+> type diffusion region 25 for a bit line and an N<+> type diffusion region 26 for control are formed in an element region surrounded by a field oxide film 22 in the surface of a P type semiconductor substrate 21. A floating gate 29 consisting of polycrystalline silicon through extremely thin oxide films 27, 28, a gate oxide film 30 and a select gate 31 are shaped. A common potential line 34, a diffusion region 25 for the bit line and the bit line 36 are formed on a CVD oxide film 32. Withstanding voltage between N type impurity diffusion layers is increased with the lowering of concentration when a distance (a) is kept constant, and the distance (a) can be set to a small value with the reduction of impurity concentration when withstanding voltage is kept constant. |
