In a method for manufacturing a micromechanical membrane structure, a doped area is created in the front side of a silicon substrate, the depth of which doped area corresponds to the intended membrane thickness, and the lateral extent of which doped area covers at least the intended membrane surface area. In addition, in a DRIE (deep reactive ion etching) process applied to the back side of the silicon substrate, a cavity is created beneath the doped area, which DRIE process is aborted before the cavity reaches the doped area. The cavity is then deepened in a KOH etching process in which the doped substrate area functions as an etch stop, so that the doped substrate area remains as a basic membrane over the cavity.