We consider the field theoretical approach as a new method to describe electrified interfaces. We derive Poisson-Boltzmann equations within our approach as a starting point for the non-linearized Gouy-Chapman theory. We discuss an extension beyond this regime adding a quadratic and a non-local contribution to the effective Hamiltonian. We analyse a Gaussian model and present the resulting charge and density distributions at the interface. We analyse the physical content of the parameters which characterize this intermediate level description.