| 摘要 |
PURPOSE:To enable soft errors due to radioactive rays such as alpha rays to be avoided with a simple construction, by forming second-conductivity-type regions serving respectively as a charge storing region and as a bit line such that they are surrounded by a high-concentration region having a first type of conductivity. CONSTITUTION:A semiconductor substrate 1 having a first type of conductivity is provided with a high-concentration region 12 having the first type of conductivity and a higher concentration than that of the semiconductor substrate 1, using a first resist mask 13. Then, the first resist mask 13 is developed again to form a second resist mask 14. Using this second resist mask 14, a second-conductivity-type region 6 as a charge storing region and a second-conductivity-type region 7 as a bit line are formed such that they are surrounded by the high-concentration region 12. For example, a semiconductor substrate 1 having an isolating insulation film 8 is provided with a first resist mask 13, and a P<+> region 12 having a higher concentration than that of the semiconductor substrate 1 are formed by implanting and diffusing an P<+> type impurity. The resist mask is then developed again to form a second resist mask 14 so that it has different configurations from those of the first resist mask 13. N<+> regions 6 and 7 are formed by implanting and diffusing an N<+> type impurity. |
