We present in this work the growth of magnetic tunnel junctions on Si(001) substrates using a template layer technique and the implementation of the layer-by-layer method to form the oxide barrier layer. By using a Co2Si template layer formed by deposition of Co on Si at a temperature of ~300 °C, we show that it is possible to considerably reduce the reaction between transition metals with Si substrate. We have also investigated the growth of alumina (Al2O3) barrier layer by an alternative layer-by-layer deposition method, which consists of successive cycles of molecular-beam deposition of an Al monolayer and oxidation under an O2 flux at room temperature. Numerous Co(Fe)/AlOx/ NiFe tunnel junctions have been fabricated on Si(001) substrates. The oxidation kinetics, the surface morphology as well as the interface roughness and abruptness are studied by means of Auger profilometry, transmission electron microscopy and atomic force microscopy. We show that it is possible to realize a uniform and homogeneous nanometer-thick AlOx layer with smooth and sharp interfaces. Current-voltage and Kerr effect measurements are also used to investigate the electric and magnetic properties of these junctions.