  A novel interaction mechanism in MOSFET structures and $GaAs/AlGaAs$
hetero-junctions between the zone electrons of the two-dimensional (2D) gas and
the charged traps on the insulator side is considered. By applying a canonical
transformation, off-diagonal terms in the Hamiltonian due to the trapped level
subsystem are excluded. This yields an effective three-particle attractive
interaction as well as a pairing interaction inside the 2D electronic band. A
type of Bethe- Goldstone equation for three particles is studied to clarify the
character of the binding and the energy of the three-particle bound states. The
results are used to offer a possible explanation of the Metal-Insulator
transition recently observed in MOSFET and hetero-junctions.
