Hot carrier instability (HCI) in a floating body cell (FBC) has been investigated. The FBC is a dynamic random-access memory (DRAM) made entirely of a silicon-on-insulator (SOI)-MOS without a capacitor. For FBC realization, there is an influence of a physical phenomenon different from the normal MOS because of its structural and operational characteristics of SOI-MOS. The difference between bulk and SOI-MOS is not yet clear, especially for HCI. In this study, we clarified the importance of the structural and geometrical factors of the FBC cell transistor and the SOI-specific floating body effect in the HCI regime of FBCs.