In this letter, a novel structure of the polycrystalline silicon thin-film transistors (TFTs) with a self-aligned gate and raised source/drain (RSD) formed by the damascene process has been developed and investigated. Comparing with the conventional coplanar TFT, the proposed RSD TFT has a remarkable lower OFF-state current (177 to 6.29 nA), and the ON/OFF current ratio is only slightly decreased from 1.71 × 10 7 to 1.39 × 10 7 . Only four photomasking steps are required. This novel structure is an excellent candidate for further high-performance large-area device applications. Index Terms-Damascene process, four masks, on/off current ratio, polycrystalline silicon thin-film transistor (poly-Si TFT), raised source/drain (RSD), self-aligned gate, thin channel.

In this letter, a novel structure of polycrystallinesilicon thin-film transistors (TFTs) with self-aligned raised source/ drain (SARSD) and a thin channel has been developed and investigated. In the proposed structure, a thick SD and a thin active region could be achieved with only four mask steps, which are less than that in conventional raised SD TFTs. The proposed SARSD TFT has a higher ON-state current and a lower OFF-state leakage current. Moreover, the ON/OFF current ratio of the proposed SARSD TFT is also higher than that of a conventional coplanar TFT.Index Terms-Four masks, ON/OFF current ratio, polycrystalline-silicon thin-film transistor (poly-Si TFT), self-aligned raised source/drain (SARSD), thin channel.