A micro-heater element for a MEMS sensor device, envisages, in a single conductive layer: an outer ring, defining inside it a window; a heat-diffusion structure, arranged within the window, separated from the outer ring by a first separation gap; and connection elements, arranged between the heat-diffusion structure and the outer ring, and designed to connect the heat-diffusion structure to the outer ring. The outer ring is designed to dissipate energy upon passage of an electric current, and the heat-diffusion structure is designed to distribute, within the micro-heater element, the heat that is transferred by the outer ring through the connection elements.