Field enhancement of omega-shaped-gated poly-Si TFT SONOS memory fabricated by a simple sidewall spacer formation

A novel omega-shaped-gated (Ω-Gate) poly-Si thin-film-transistor (TFT) silicon–oxide–nitride–oxide–silicon (SONOS) nonvolatile memory devices fabricated with a simple process have been proposed for the first time. The Ω-Gate structure inherently covered two sharp corners manufactured simply via a sidewall spacer formation. Due to the sharp corner geometry, the local electric fields across the tunneling oxide could be enhanced effectively, thus improving the memory performance. Based on this field enhanced scheme, the Ω-Gate TFT SONOS revealed excellent program/erase (P/E) efficiency and larger memory window as compared to the conventional planar (CP) counterparts. In addition, owing to the better gate controllability, the Ω-Gate TFT SONOS also exhibited superior transistor performance with a much higher on-current, smaller threshold voltage, and steeper subthreshold swing. Therefore, such an Ω-Gate TFT SONOS memory is very promising for the embedded flash on the system-on-panel applications.