A negative differential resistance (NDR) diode and a memory cell incorporating that NDR diode are provided. The NDR diode comprises a p-type germanium region in contact with an n-type germanium region and forming a germanium pn junction diode. A first gate electrode overlies the p-type germanium region, is electrically coupled to the n-type germanium region, and is configured for coupling to a first electrical potential. A second gate electrode overlies the n-type germanium region and is configured for coupling to a second electrical potential. A third electrode is electrically coupled to the p-type germanium region and may be coupled to the second gate electrode. A small SRAM cell uses two such NDR diodes with a single pass transistor.