In this thesis, we propose a new thin-film transistor with trenched body and airgap-insulated structure (AITFT) for one-transistor dynamic random access memory (1T-DRAM) applications and investigate the influence of different materials on the sensing current window and retention time. Its basic operation mechanisms are based on the impact ionization and floating body effects. Due to the generated holes storing in the pseudo neutral region, the threshold voltage (Vth) is lower, resulting in a high drain current for state ¡§1¡¨. So we can recognize the data by sensing the difference of the drain current. According to the ISE TCAD 10.0 simulations, owing to the design of trench and airgap-isolation structure, the AITFT can enhance about 212% sensing current window and 42% retention time compared with the conventional TFT at the channel length of 150 nm and temperature of 300K conditions. Also, owing to the source/drain-tie, the generated heat can be dissipated quickly from the source/drain to the substrate thus the thermal instability is improved. In other words, the AITFT can improve the thermal reliability but without losing control of the short-channel effects.