| 摘要 |
A DRAM semiconductor device has: a semiconductor substrate with one surface; a first well and a second well respectively formed in a first region and a second region in areas of the one surface of the semiconductor substrate, the first and second wells each having a local maximum of a first conductivity type impurity concentration at a depth position apart from the one surface of the semiconductor substrate, and one of a depth and the first conductivity type impurity concentration of the local maximum of the second well is larger than that of the first well, and the other is at least equal to that of the first well; a memory cell formed in the first well; and a peripheral circuit for the memory cell formed in the second well. A DRAM semiconductor device is provided whose refresh characteristics are improved without deteriorating other characteristics.
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