  The tetrad gauge invariant theory of the free Dirac field in two special
moving charts of the de Sitter spacetime is investigated pointing out the
operators that commute with the Dirac one. These are the generators of the
symmetry transformations corresponding to isometries that give rise to
conserved quantities according to the Noether theorem. With their help the
plane wave spinor solutions of the Dirac equation with given momentum and
helicity are derived and the final form of the quantum Dirac field is
established. It is shown that the canonical quantization leads to a correct
physical interpretation of the massive or massless fermion quantum fields.
