The model of charge carrier transport in ferromagnet/wide-gap semiconductor/ ferromagnet nanostructure based on two-band Franc-Keine model and phase function method was proposed. It is determined that tunneling barrier, formed by the gap of wide-gap semiconductor, does not represent potential step, but the energy band gap. Its upper border is the bottom of the conduction band EC, and the bottom part is the top of the valence band EV. Inside this zone wave vector of the electron is an imaginary value. According to the dispersion law, states located in the midgap sustain the largest attenuation. That is why when the Fermi level of the analyzed structure lies in the bottom part of the band-gap, bias voltage V shifts levels of the tunneling electrons to a low barrier area. This shifting is thereason of the tunneling current reduction and leads to the negative differential resistance effect. It is shown that areas of the negative differential resistance effect appear at the current-voltage bias dependence at qV> EF. Here areas of negative differential resistance should be expected at the voltage values higher than Fermi energy value of the emitting electrode for the zone electrons with the spin-up.