Stacked capacitor dynamic random access memory(DRAM) cells with both NMOS and PMOS cell transistors(Lg=0.4µm) were fabricated on ultra-thin SIMOX(separation by implantation of oxygen) substrates, and the data retention time was compared with that of a bulk counterpart. A DATA retention time of 550 sec(at 25 ) could be achieved using ultra-thin SIMOX substrates, which is 6 times longer than that using the bulk substrate. A stacked capacitor cell with a PMOS cell transistor on an ultra-thin SIMOX substrate is very attractive and promising for future giga-bit DRAM cells.