An insulation layer system, in particular for gas sensors, is proposed, having at least one electrically conductive solid-electrolyte layer (10), an electrically conductive layer (20) and at least one electrically insulating layer (13) between the solid-electrolyte layer (10) and the electrically conductive layer (20). The material of the insulating layer (13) contains, prior to sintering, pentavalent metal oxides of niobium or tantalum as an additive, it being possible for the additive to diffuse into the adjoining solid-electrolyte layer (10) during sintering.