We examine the possibility of excitonic superconductivity at a metal - semiconductor interface. An ab initio RPA calculation of the screened Coulomb electron - electron interaction is performed for the silicon - jellium multilayer model. The superconducting kernel for this multilayered system is found to be positive in the whole frequency range considered. We show that the inclusion of local field effects does not change the sign of the kernel and thus does not enhance the excitonic mechanism.