A microelectromechanical sensor includes: a supporting body, containing semiconductor material; and a cap, of semiconductor material, coupled to the supporting body and having an internal surface arranged facing the supporting body and a plurality of inlet holes. The sensor further includes a sensing structure, comprising a measuring chamber and a sensitive element, the sensitive element being formed at least partially in the supporting body and facing the measuring chamber; fluidic paths configured to couple the sensing structure with the environment external to the sensor through the inlet holes, and having an access section to the measuring chamber; and trapping structures defined in the supporting body. The trapping structures are in communication with respective fluidic paths and extend in the supporting body at least partially at a greater distance, from the internal surface of the cap, with respect to the access section of each fluidic path.