Scaling considerations of conventional DRAMs lead to recent developments of capacitor-less, single-transistor (1T) DRAM based on the floating-body effects in SOI transistors. Several options (Z-RAM and TTRAM) are reviewed and discussed in terms of operation mechanisms, performance and scaling. We also describe a new concept of 1T-DRAM (named MSDRAM) simple to fabricate, program and read. Its basic mechanism is the meta-stable dip (MSD) hysteresis effect which takes advantage of the coupling between front and back interfaces in SOI transistors. Systematic measurements show that MSDRAMs are suitable for low-power applications as they exhibit negligible off-state current, long retention time and scalability. (C) 2007 Elsevier Ltd. All rights reserved.