The electron foreshock located upstream of the shock front is populated with electrons having interacted with the shock and then are reflected back with an high energy gain. These backstreaming particles propagate along the interplanetary magnetic field into the solar wind and are associated to an important wave activity. One of the important unresolved problem is the exact origin of these high-energy backstreaming charged particles. It is widely accepted that the shock back-streaming electrons have been accelerated through a fast-Fermi interaction (Type 1) but such oversimplified picture has to be strongly modified when the internal structure and the nonstationarity of the shock front are taken into account. The purpose of the present work is to identify the different sources of backstreaming electrons. This work is based on the use of two dimensional PIC simulation of a curved shock, where full curvature effects, time of flight effects and both electrons and ions dynamics are fully described by a self consistent approach. The analyis is restricted within a quasi-perpendidular shock with 90° ≥ ΘBn ≥ 45°, where ΘBn is the angle between the shock normal and the upstream magnetostatic field. These simulations allow to reproduce salient features of a curved supercritical shock both for particles and for electromagnetic fields (Savoini et Lembege, 2001). Electromagnetic precursor emitted by the shock front as ΘBn decreases is observed and parallel electrostatic turbulence is evidenced in conjonction with the reflected electrons. In complement to previous works, present results evidence almost three -instead of two- different classes of electrons which contribute to the backstreaming population, depending on their interaction with the shock front: (i) the mirrored reflected electrons (Fermi type 1) in the shock front, (ii) the resonant population trapped within the parallel electrostatic potential well in the overshoot region and which gains enough energy to escape back into the upstream region and (iii) the leaked electrons which penetrate more deeply into the downstream region and are also locally accelerated before reaching appropriate conditions at the shock front to escape back into the upstream region. The third population includes particles penetrating the shock front around ΘBn=90° but escaping from the shock front at strongly oblique direction (around 50°). This explains why these so called leaked electrons have not been observed in previous simulations (Savoini et Lembege; 2001) restricted to a narrower angular range (90° ≥ ΘBn ≥ 45°). Details on their acceleration mechanisms will be presented and compared with previous works. Reference : Savoini Ph. et B. Lembège, " Two-dimensional simulations of a curved shock: Self-consistent formation of the electron foreshock ", J. Geophys. Res., Vol. 106, pp 12975-12992, 2001.