A micro-hotplate device, useful in catalytic high-temperature chemical sensors, micro-chemical reactors and as infra-red source, in particular at temperatures above 600 DEG C, comprises a thin film resistive heater (1) made of a refractory metal silicide selected from silicides of tantalum, zirconium, tungsten, molybdenum, niobium and hafnium, the silicide having a polycrystalline structure obtainalble at temperatures above 600 DEG C. The thin film resistive heater (1) is encapsulated between insulating layers (2a, 2b) forming a sandwich structure (5) and is located in a membrane (7) over an aperture (6) in a silicon substrate (4). The device is producible by standard micromachining techniques.