The present invention concerns a device for heating a sample by microwave radiation comprising a source of microwave radiation, a first waveguide for guiding said microwave radiation to an applicator space adapted to receive said sample to be heated, wherein said applicator space is defined by a terminal portion of said first waveguide and an initial portion of a second waveguide extending from said terminal portion of said first waveguide and being arranged at an angle with respect to said first waveguide.