In this article the field electron emission from:a semiconductor (with special emphasis on silicon) occurring through a thick: oxide layer is considered. The oxide thickness is,taken:large enough (as compared to the electron mean free path) to allow for transport effects. The electrons are injected from the conduction band of the semiconductor into the conduction band of the oxide, through the interfacial potential barrier. Finally they are emitted through the oxide-vacuum interface; Owing to the small density of conduction: electrons in the oxide layer, the electric field deeply penetrates it. For a more refined model, field penetration into the-base semiconductor can also be considered. Comparative computations of the emission current density are performed for these two models. No essential differences are found in the high field range. For relatively low field Strength, however, significant improvement can be obtained by considering field:penetration into the semiconductor. These-observations may be of use in designing electron field emission devices. Vacuum Society. [S0734-211X(99)00402-3].