A thick-film strain-sensing structure for a media-compatible, high-pressure sensor. The strain-sensing structure generally includes a metal diaphragm, at least one electrical-insulating layer on the diaphragm, an interface layer on the electrical-insulating layer, and at least one thick-film piezoresistor on the interface layer for sensing deflection of the diaphragm. The interface layer and the electrical-insulating layers are preferably formed by thick-film processing, as done for the piezoresistors. For compatibility with the metal diaphragm, the electrical-insulating layer has a CTE near that of the diaphragm. The interface layer is formulated to inhibit and control diffusion of the electrical-insulating layers into the piezoresistors. For this purpose, the interface layer is formed from a composition that contains, in addition to a suitable organic media, alumina, zinc oxide, and at least one glass frit mixture comprising lead oxide, a source of boron oxide such as boric acid, silica and alumina. Additional constituents of the interface layer preferably include titania, cupric oxide, manganese carbonate as a source for manganese monoxide, and cobalt carbonate as a source of cobalt oxide.