A 128Mb SOI DRAM with FBC (floating body cell) has been successfully developed for the first time. Two technologies have been newly implemented. (i) In order to realize full functionality and good retention characteristics, the well design has been optimized both for the array device and the peripheral circuit. (ii) Cu wiring has been used for bit line (BL) and source line (SL), which leads to increasing the signal of the worst bit in the array and also realizes the full compatibility with 90nm CMOS technology