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Low-voltage high-density embedded RAMs (e-RAMs) in the nanometer era are described, with a focus on RAM cells and peripheral circuits. First, challenges and trends in low-voltage e-RAMs are described based on the signal-to-noise ratio problem of RAM cells, then leakage and speed-variation problems of peripheral circuits. Next, state-of-the-art low-voltage e-DRAMs and e-SRAMs are investigated, mainly focusing on cell structures and leakage-reduction circuits. Finally, future prospects for low-voltage e-RAMs are discussed.