  Two dimensional InAs/GaAs quantum ring (QR) is considered using the effective
potential approach. The symmetry of QR shape is violated as it is in the
well-known Bohigas annular billiard. We calculate energy spectrum and studied
the spatial localization of a single electron in such QR. For weak violation of
the QR shape symmetry, the spectrum is presented as a set of quasi-doublets.
Tunneling between quasi-doublet states is studied by the dependence on energy
of the states. The dependence is changed with variation of the QR geometry that
is related to the eccentricity of the QR. An interpretation of the experimental
result obtained in [1] is proposed. We show that the "chaos-assisted tunneling"
effect found in this paper can be explained by inter-band interactions occurred
by anti-crossing of the levels with different "radial" quantum numbers.
