A multigate polycrystalline-silicon (poly-Si) thin-film transistor (TFT) is a recently popular topic in the field of Si devices. In this study, self-aligned planar metal double-gate poly-Si TFTs consisting of an embedded bottom metal gate, a top metal gate fabricated by a self-alignment process, and a lateral poly-Si film with a grain size greater than 2µm were fabricated on a glass substrate at 550°C. The nominal field-effect mobility of an n-channel TFT is 530cm²/Vs, and its subthreshold slope is 140mV/dec. The performance of the proposed TFTs is superior to that of top-gate TFTs fabricated using equivalent processes.