The charging and discharging processes in amorphous silicon nitride (a-SiNx) by using the Metal/a-SiNx/SiO2/Si structure (MNOS) were experimentally and theoretically considered. The tunnel-thick (10 nm) SiO2 layer and metal gates with different work functions were used. This made it possible to separate the electron and hole components of the currents during the charging voltage action. The discharge times in the MNOS-structure at high temperatures (400 K) and the same “pulling” voltage coincide for electrons and holes. The charge transport is described by the multiphonon mechanism of trap ionization. In the discharging mode, the parameters of electron and hole traps in SiNx were determined and they turned out to be equal, and that indicate the amphoteric nature of traps in SiNx.