| 摘要 |
PURPOSE:To obtain a DRAM device having a wide circuit margin, strong soft- error resistance and the excellent holding characteristics of a memory by forming a trench, the inner diameter of which is made larger in a high- concentration impurity layer than in a low-concentration impurity layer, and a capacitor formed onto the inner surface of the trench. CONSTITUTION:P-type silicon epitaxial layers 12 and P<+> type silicon epitaxial layers 13 are shaped alternately onto a P<+> type silicon substrate 11. Two trenches 14 are formed to the layers 12, 13 in the vertical direction, and polysilicon 18 is buried onto the inner surfaces of the trenches 14 through oxide films 17. The size (thickness) of the trench 14 is increased in the P<+> type epitaxial layer 12 in high concentration, and reduced in the P-type epitaxial layer 13 in low-concentration. A transistor 21 is shaped onto an upper surface by an N<+> type silicon layer, a gate oxide film, etc. Accordingly, a memory cell is formed into the epitaxial layers, thus extremely decreasing troubles of soft-error. |
