Ge2Sb2Te5 (GST) has been widely studied for PRAM as reversible phase change material. GST is expected to reduce RESET (crystalline → amorphous) operation power, which is one of important issues for PRAM technology. In order to investigate the effect of nitrogen doping on electrical switching characteristics, we fabricated two kinds of PRAM cells with nitrogen-doped (N-doped) and un-doped GST, which were different bottom electrode contact size (0.80~1.00 ). N-doped GST PRAM cells have higher dynamic resistance with small sized bottom electrode contact and lower RESET voltage (about 1.2 V, 50 ns) than un-doped GST PRAM cells (about 1.6 V, 50 ns). The resistance switching ratio (RRESET to RSET) was about 100. The results of this study indicate that nitrogen doping into GST film and smaller size of bottom electrode contact reduce RESET power for PRAM operation.