Membrane (24) of a shell (20) of a pressure sensor, having an upper and lower chamber (34, 23), wherein the membrane is made by a support wall (36) and a cap (41) having an upper and lower sheets (31, 32), the support wall having a central aperture (33), the support wall separating but for its central aperture the lower from the upper chamber, the lower sheet (32) having a central aperture (38), edges of the central apertures (33, 38) of the support wall (36) and of the lower sheet (32) respectively being welded to one another, peripheries (37) of the upper and lower sheet (31, 32) being welded to one another so that a volume (40) is present between said upper and lower sheets (31, 32), said volume being in the upper chamber (34) and communicating through the central apertures (33, 38) of the support wall (36) and of the lower sheet (32) respectively, with the lower chamber (23).