Thin selective chemical vapor deposited tungsten films are evaluated as a barrier metal for reaction between Al–1%Si electrode and Si substrate. Change in contact resistance and junction leakage current after annealing at 500 °C in N2are measured. It is found that an increase of contact resistance at a very small contact hole of 2.25 μm2is very slight. On the other hand, contact resistance in Al–1%Si electrode increases to one or two magnitudes with annealing of 210 min. Junction leakage current in a tungsten electrode is almost the same as that in Al–1%Si electrode. And it is also found that a thin tungsten layer protects the diffusion of aluminum into the Si substrate. From these results, it is concluded that thin selective chemical vapor deposited tungsten films have a good barrier effect for the reaction between Al–1%Si electrode and Si substrate.