An improved semiconductor pressure sensor of the silicon diaphragm type is disclosed. The sensor includes a pressure sensor device composed of a substrate of monocrystalline silicon, a diffused resistive layer formed on one surface of the substrate and a cavity formed in the other surface to create a thin-walled area that includes the diffused resistive layer with the cavity surrounded by a thick-walled leg portion. A hermetic sealable cap covers the one surface of the sensor device. A conductive diffused region from which an electrical signal can be picked up is provided in the leg portion electrically connected to the diffused resistive layer.