Apparatus for vaporizing and/or superheating of a medium

A device is used for evaporating and/or superheating a medium, in particular a hydrocarbon or a hydrocarbon/water mixture for a gas generation system of a fuel cell system, with a heat exchanger. The heat exchanger has in its medium-side region at least one foil pair (5) and respectively one inlet opening (2) and outlet opening (3), which are each connected to a medium space (7) between the two foils (5a, 5b) of the at least one foil pair (5). The medium-side region is in heat-conducting contact with a heat transfer medium-side region (10). The medium space (7) is formed between the two foils (5a, 5b) by indentations (8) introduced on the side of at least one of the foils facing the medium. The surface of at least one of the foils (5a, 5b) of the at least one foil pair (5) facing away from the medium is provided with heat transfer fins (6), wherein the height of the heat transfer fins is greater than the depth of the indentations.