Method and realization of a grid surface of an electrochemical sensor integrated, is a field-effect transistor and sensitive to alkaline earth species and obtained sensor.

The invention concerns chemical detectors. The process involves grafting the surface using a grafting product in order to create grafts on some at least of the sites; preparing the phosphonate-based iono-sensitive molecules; and making operative some at least of the grafts with the aid of the iono-sensitive molcules. Application in detectors for measuring the degree of water hardness.