The manifestations of semiconductor depletion and depolarizing effects in switching and fatigue are studied and compared. It is shown that these effects play important but quite different roles in switching. The depletion effect strongly influences the values of the coercive field, E(c), and is responsible for its film-thickness dependence. The depolarizing effect influences significantly other parameters of the hysteresis loops. It is shown that the inverse thickness dependence of E(c) can not be attributed to the presence of a non-switching layer. Contribution of the effects in question to fatigue of the loop parameters is discussed.