Abstract: A method for fabricating a solid state semiconductor gas sensor and the semiconductor sensor itself for use in equipment detecting small amounts of H.sub.2 S. The method of sensor fabrication comprises spray deposition of a mixture of metal oxides mixed together with various metal and non-metal materials which serve in the finished product as activators, dopants, and/or film binder materials, and including in suspension a molecular sieve material, for enhancing porosity on a scale of molecular dimensions in the finished sensor. All of the foregoing materials are suspended in a suitable solution and preferably sprayed onto a heated insulating substrate to form the finished product. The example sensor, capable of selective detection of H.sub.2 S in air and a sensitivity of less than 1 PPM (part per million), is comprised of a platinum activated alumina, tin oxide, and zeolite molecular sieve material.