The objective is to theoretically and experimentally investigate and quantify plasma-dynamics effects, including performance degradation and long-term failure modes, for micro- and nano-structures with RF fields in the MHz to 100s GHz. Intellectual Merit: Micro/nano-gaps are common in a wide variety of RF MEMS such as tunable filters, varactors, and resonators. High RF fields may induce gas breakdown and ionization leading to performance degradation and/or failure in many of these devices. Moreover, conditions encountered in many MEMS lead to an entirely new type of plasmas with dynamic transition between several field-emission driven discharge regimes: electron tunneling, ion enhancement and electron avalanche. As a result, we plan to 1) Develop the fundamental understanding of the key physical phenomena that govern plasmadynamics; 2) Quantify potential long-term effects/failure modes of microplasma in micro/nano-gaps and the induced failure modes in MEMS/NEMS; and 3) Create comprehensive, multiple-domain physics modeling and simulation framework that captures the underlying microplasma effects in a compact and efficient manner. Broader Impact: This research is expected to have a transformative impact on the design and understanding of failure modes of a wide variety of N/MEMS devices. Furthermore, besides integrating our research into curricula activities, we plan to make extensive use of the memsHUB web portal to disseminate results from this study to the MEMS community through online simulation tools. This is expected to be critical in bridging the gap between fundamental plasma science and microsystems engineers. We also plan to support undergraduate students efforts and attract/retain U.S. minority students.