A method for thinning a structure of at least two assembled wafers, where one of the wafers includes channels on its surface facing the other wafer. In order to cause thinning of the structure, a fluid is introduced into the channels in a supercritical state and the fluid is passed from the supercritical state into the gaseous state. The channels do not open to the outside of the structure, such that the method further includes forming at least one access opening to the channels from the outer surface of the structure and before introducing the fluid in the supercritical state.