An oscillatory dependence of the drain current on the drain voltage is found in a nanostructure consisting of two crossing semiconductor carbon nanotubes that are suspended over a dielectric trench, which is backed by a doped silicon substrate that acts as a gate. Alternating positive and negative differential resistance regions are generated as a function of the drain-source voltage values and can be slightly shifted by the gate voltage. Moreover, the negative differential resistance is retrieved in a large bandwidth, of up to 100 MHz, when the structure is excited with ac signals. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3138815]