NOVELTY - The device (20) comprises an electronic device (12) having a hot spot having a dynamically operated architecture, a composite thermal capacitor (14) disposed locally in thermal communication with the hot spot of the electronic device, an active regeneration cooling device (16), and an external heat sink (18) present in thermal communication with the active regeneration device. The composite thermal capacitor includes a phase change material imbedded into a matrix of a high thermal conductivity material, where the heat from the hot spot is stored by the phase change material.    USE - Used as a device including a computer chip, an electronic component, a display, an engine, a fuel cell or other power generation device such as solar cell, a chemical reactor, a light source and a microprocessor.    ADVANTAGE - The device has increased local thermal capacitance, and excellent heat dissipation characteristics.    DETAILED DESCRIPTION - The device (20) comprises an electronic device (12) having a hot spot having a dynamically operated architecture, a composite thermal capacitor (14) disposed locally in thermal communication with the hot spot of the electronic device, an active regeneration cooling device (16), and an external heat sink (18) present in thermal communication with the active regeneration device. The composite thermal capacitor: includes a phase change material imbedded into a matrix of a high thermal conductivity material, where the heat from the hot spot is stored by the phase change material; is present in thermal communication with the hot spot of the electronic device using a structure consisting of through-silica vias, a high conductivity slab, a heat pipe, a fluidic loop, a solid state heat pump and/or an intermediate electronic device; and has a first area and a second area. The phase change material consists of a solid-to-solid phase change material, a solid-to-liquid phase change material, a solid-to-gas phase change material, and a liquid-to-gas phase change material. A ratio of the phase change material to the high thermal conductivity material is 1:100-1:1. The electronic device consists of a two-dimensional semiconductor chip stack, a three-dimensional semiconductor chip stack, a multi-core semiconductor chip, a memory device, application specific integrated circuits, system-on-a-chip, a microelectronic chip, an optoelectronic chip, a hybrid optoelectronic/microelectronic chip, a memory device, analog or radio frequency micro devices, system on a package, biochips, medical or electronic imaging devices, and on chip power management devices. The active regeneration cooling device is present in thermal communication with the composite thermal capacitor, where the heat from the composite thermal capacitor is dissipated by the active regeneration cooling device, and consists of a solid state cooling device. The first area includes the phase change material and the second area includes the high thermal conductivity material. The first area includes portions. Each portion has the second area as a boundary. The first and second areas are present in thermal communication between each other. Each portion of the first area has a cross-section consisting of a polygonal cross-section, a circular cross-section, circular cross-section and/or annular cross section, and an outer boundary defined by the second area. The dynamically operated architecture is a three dimensional chip stack. The phase change material is a metal and a eutectic alloy.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic view of a device comprising electronic device and capacitor.    Electronic device (12)    Composite thermal capacitor (14)    Active regeneration cooling device (16)    External heat sink (18)    Device. (20)