The present disclosure relates to a semiconductor device including an oxygen gettering layer between a group III-V compound semiconductor layer and a dielectric layer, and a method of fabricating the semiconductor device. The semiconductor device may include a compound semiconductor layer; a dielectric layer disposed on the compound semiconductor layer; and an oxygen gettering layer interposed between the compound semiconductor layer and the dielectric layer. The oxygen gettering layer includes a material having a higher oxygen affinity than a material of the compound semiconductor layer.