<p>A resin substrate which comprises a resin layer and a surface layer formed on a surface of the resin layer. The surface layer is a layer comprising silicon nitride as the main ingredient and deposited by the chemical vapor-phase growth method. In the interface between the resin layer and the surface layer, when the difference between the maximum nitrogen concentration in the surface layer and the steady-state nitrogen concentration in the resin layer is taken as 100%, then the interfacial region over which the nitrogen concentration therein changes from 80% to 20% has a thickness of 25 nm or smaller. The surface layer has an average surface roughness (Ra) of 1 nm or less. This resin substrate combines water-vapor-barrier properties with flatness.</p>
