A new family of electrochemical gas sensors based on the use of thin and thick film technologies has been under study in our Laboratory for some years. This microelectronics approach allowed us to design solid state devices for oxygen and hydrogen detection. Our experimental results evince two major interests, besides those associated with sensor miniaturization, lower price, reliability, etc.:

(1) Wide variety of available materials and substances, local modification of their composition and associated properties using techniques such as thermal diffusion and ion implantation.

(2) Possible creation of complex functions using different multi-layered geometries; for example, the catalytic activity of a platinum electrode, for the CO/O2 reaction, may be modified by changing thickness, texture and partial capping of this electrode.

Two types of new sensors using this approach are described: a zirconia-based oxygen sensor for combustion control and a hydrogen sensor working at room temperature. The experimental behaviour of these devices is presented and discussed.