A bolometric heat detector having an active part composed of at least two coplanar electrodes (8, 10) placed in electrical contact with a first thin semiconducting layer (6), doped by a first doping agent with a first type of conductivity. There is a second thin semiconducting layer (4) doped like the first layer or undoped, and a third thin semiconducting layer (2) doped by a second doping agent with a second type of conductivity opposed to the first. The second layer (4) is placed between the first (6) and the third (2) layers.