We report in this article a feasibility study of ultra-thin device packages. These packages combine thin integrated circuit chips, thin flex circuitry, and adhesive flip-chip technologies. Using this novel packaging concept, we constructed 512 kb SRAM memory modules that were less than 150 micron thick. Even more profound, the package was flexible enough to conform to nonplanar surfaces. This unique property can lead to new applications that would not be feasible otherwise and extend the reach of electronics into brand new areas. Two of these ultra-thin modules were stacked to construct a 3-D package with 1 Mbyte of memory capacity that is approximately 30 times thinner and 30 times lighter than a conventionally packaged device.Index Terms-Adhesive flip-chip bonding, flexible, packaging, thin IC, 3-D.