Heat engines provide most of our mechanical power and are essential for transportation on macroscopic scale. However, although significant progress has been made in the miniaturization of electrostatic engines, it has proven difficult to reduce the size of liquid or gas driven heat engines below 10^7 um^3. Here we demonstrate that a crystalline silicon structure operates as a cyclic piezoresistive heat engine when it is driven by a sufficiently high DC current. A 0.34 um^3 engine beam draws heat from the DC current using the piezoresistive effect and converts it into mechanical work by expansion and contraction at different temperatures. This mechanical power drives a silicon resonator of 1.1x10^3 um^3 into sustained oscillation. Even below the oscillation threshold the engine beam continues to amplify the resonator's Brownian motion. When its thermodynamic cycle is inverted, the structure is shown to reduce these thermal fluctuations, therefore operating as a refrigerator.Comment: Updated version after publication to make it almost identical to the Nature Physics article. During the review process the preprint v1 was merged with part of the results from arXiv:0904.3748 (please check this manuscript for more details on the measurements and simulations

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Hot-carrier degradation phenomena in field-plate assisted reduced surface field (RESURF) devices caused by high voltage off-and on-state stressing have been investigated. The device I-V characteristics are analyzed and modeled in detail. It is shown that via noninvasive low-voltage leakage characterization the surface generation velocity profiles after (high-voltage) stress can be extracted, enabling I-V degradation predictions across wide temperature ranges.13.4.2 IEDM12-312

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