| 摘要 |
It is an object to integrate storing functions at a high density and make it possible to perform a stable operation even at a low power supply voltage. A MOS transistor including a gate electrode and an n-type impurity region serving as a source-drain has a memory capacitor comprised by a dielectric film, a conductor, and an n-type impurity region opposing to the conductor through the dielectric film in a first trench formed in a p-type epitaxial layer beneath the gate electrode. With this structure, an area occupied by the MOS transistor and the memory capacitor can be minimized. Each unit memory cell is a two-transistor memory cell in which the drain and source of a MOS transistor supply a pair of complementary signals to a detection circuit. For this reason, a storing operation can be made reliable, and a stable operation can be realized, especially, at a low voltage.
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