A novel thin-film transistor with self-aligned field induced drain

In this letter, a novel thin-film transistor with a self-aligned field-indu ced-drain (SAFID) structure is reported for the first time. The new SAFID T FT features a self-aligned sidewall spacer located on top of the drain offs et region to set its effective length, and a bottom gate (or field plate) s ituated under the drain offset region to electrically induce the field-indu ced-drain (FID). So, unlike the conventional off-set-gated TFTs with their effective FID length set by two separate photolithographic masking layers, the new SAFID is totally immune to photomasking misalignment errors, while enjoying the low off-state leakage as well as high turn-on characteristics inherent in the FID structure. Polycrystalline silicon TFTs with the new SA FID structure have been successfully fabricated with significant improvemen t in the on/off current ratio.