  Landau's theory of Fermi liquids is generalized by incorporating the de
Broglie waves diffraction. A newly derived kinetic equation of the Fermi
particles is used to derive a general dispersion relation and the excitation of
zero sound is studied. A new mode is found due to the quantum correction. It is
shown that the zero sound can exist even in an ideal Fermi gas. We also
disclose a new branch of frequency spectrum due to the weak interaction.
