A 3D packaging technology for 4 Gbit DRAM has been developed. It is targeting to realize 4Gb density DRAM by stacking 8-DRAM chips into one package. Interconnect between stacked chips will be done by through-silicon-via for the requirement of 3Gbps operation. Key process technologies for chip stacking are through-silicon-via formation, wafer back side process and micro-bump bonding. These chip-stacking processes have been developing using TEG, which can evaluate electrical characteristics.