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Polycrystalline silicon thin-film transistors (TFTs) can be improved by integrating DRAM on chip. However, the TFT's poor capacitance means that traditional DRAMs are infeasible, because they require a capacitor. An alternative, the one-transistor DRAM (1T-DRAM), is promising because it avoids the capacitor by instead storing the logical value as holes trapped in the body region. This letter proposes the use of a trenched body in a TFT to construct a 1T-DRAM. Previously, we have shown that a trenched body reduces the leakage current of a TFT. In this letter, we now show that the trenched-body TFT also works well as a 1T-DRAM device. It has a strong back-gating effect and a programming window that is more than twice as large as that of the conventional TFT.
Date of Publication: Nov. 2008