摘要 |
PURPOSE:To prevent a mulfunction from being caused by incidence of radioactive rays by a method wherein an electric charge reservoiring region and bit line region having conductivities different from that of a substrate are surrounded on the peripheries by regions with density higher than the substrate and having the same conductivity as that of the substrate. CONSTITUTION:An N<+>-region 6 as the electric charge reservoiring region of a memory cell and an N<+>-region 7 as the bit line are surrounded on the peripheries by P<+>-regions 12, 13 in higher density than a P<-> type semiconductor substrate. Whereby electrons diffused from the substrate 1, out of electrons and holes pair created in the substrate 1 by radioactive rays of alpha-ray and the like, are recombined in the regions 12, 13 and not collected in the regions 6, 7. In addition, since a potential barrier against the electrons is formed on the interface of the substrate 1 and the regions 12, 13, the electrons smaller in energy out of the electrons diffused from the substrate 1 cannot pass through the potential barrier. Accordingly, the electrons are collected in the regions 6, 7 to cause the memory information to be inverted and the mulfunctions are prevented from being caused. |