Abstract : It has been shown that when a two-dimensionnal hole gas is introduced in a semimagnetic semiconductor quantum well, a ferromagnetic phase takes place. We have elaborated structures based on II-VI semiconductors (tellurides), by Molecular Beam Epitaxy, in order to prove that it is possible to control the ferromagnetic transition. This control has been reached through an electric field applied on a pin diode, through an illumination that modify the hole density in a pip structure, and through strain and confinement in the quantum well. We have demonstrated a new way for p-type doping usinf surface acceptor states created by oxidation. We have identified the existing species and shown that the doping is very sensitive to the cap thickness.