Floating-gate memory cells having carbon nanotubes interposed between the substrate and the tunnel dielectric layer facilitate ballistic injection of charge into the floating gate. The carbon nanotubes may extend across the entire channel region or a portion of the channel region. For some embodiments, the carbon nanotubes may be concentrated near the source/drain regions. For some embodiments, the tunnel dielectric layer may adjoin the substrate in at least a portion of the channel region.