A series of Pd/SnO 2 /SiO 2 /Si heterojunction sensors were produced using magnetron sputtering method. It is found that the Pd/SnO 2 /SiO 2 /Si heterojunction exhibits ultrahigh H 2 response of ∼17363% to 1.0% H 2 at room temperature, and has fast response and recovery, excellent stability and selectivity. Therefore, this kind of heterojunction may be a promising candidate for effective H 2 detection at room temperature. The H 2 response characteristics and the optimum operating voltage of the sensors is modulated by the interface barrier potential between SnO 2 and Si, which can be understood by the interfacial energy band characteristics of the Pd/SnO 2 /SiO 2 /Si heterojunction. [ABSTRACT FROM AUTHOR]