A microelectromechanical pressure sensor structure that comprises a planar base and side walls and a diaphragm plate. The side walls extend circumferentially away from the planar base to a top surface of the side walls. The planar base, the side walls and the diaphragm plate are attached to each other to form a hermetically closed gap in a reference pressure, and a top edge of the inner surfaces of the side walls forms a periphery of a diaphragm. The diaphragm plate comprises one or more planar material layers of which a first planar material layer spans over the periphery of the diaphragm. The top surface of the side walls comprises at least one isolation area that is not covered by the first planar material layer.