More than any other single domain, device technology establishes the opportunities and limitations imposed on the high-performance system developer. The history of computer architecture is to a significant degree a sequence of enhancements to instruction set and component organization architectures in response to advances in device technologies. In preparing the possible paths toward PetaFLOPS system structures, it is essential to anticipate future trends and likely characteristics of next generation technologies. The Device Technology Working Group considered three technologies most likely to provide the basis for implementation of PetaFLOPS computing systems: advanced semiconductors, optical devices, and superconducting elements. In each case, current capabilities and projected evolutionary advances were explored. From these results, possible roles for each technology in support of PetaFLOPS computers were identified, providing a foundation and constraint space for new system design possibilities. The following summarizes the issues and findings of this working group related to each of the technologies considered. It was found that advanced semiconductor components will provide main memory and possibly processing logic; superconducting technology may provide very high-speed processor logic at very low power consumption; optical technology will provide essential capabilities in high-bandwidth intermodule interconnect and mass storage.