Method and device for the heat treatment of substrates, wherein the substrates are positioned in the vicinity of a heated, essentially flat furnace body extending over the surface of the substrate. In order to provide a reproducible treatment when treating a number of substrates successively, the temperature of the furnace body is measured so close to the surface adjacent to the substrate that the withdrawal of heat from the furnace body by the substrate can be detected. The introduction of each substrate takes place at a point in time when the temperature measured in this way is, within certain limits, equal to a desired initial treatment temperature Ttrig.