To improve the stability and robustness of a rectifier and to protect it against atmospheric influences, two semiconductor diodes in the shape of small plates or discs are disposed to hold between them a center electrode. A wire-like lead electrode is held in contact with the remaining side of one diode and the second lead electrode is cup-shaped and its walls surround the diode stack. An inwardly extending lip of the cup-shaped electrode supports a spring which exerts pressure on the enlarged tip of the first lead electrode, thus clamping the entire stack in contact. A cover plate seals the opening of the cup and a resinous mass may be applied over the cover plate to provide a hermetic seal.