NOVELTY - The device (10) has a compound semiconductor layer (11) comprising elements from different groups of a periodic table. A dielectric layer (13) is arranged on the compound semiconductor layer. An oxygen gettering layer (12) is interposed between the compound semiconductor layer and the dielectric layer. The oxygen gettering layer comprises a material with a higher affinity for oxygen than a material of the compound semiconductor layer. A passivation layer is interposed between the compound semiconductor layer and the oxygen gettering layer.    USE - Compound semiconductor device i.e. MOSFET semiconductor device, for use in a millimeter/microwave apparatus or an optoelectronic device. Uses include but are not limited to transistor, capacitor, light-emitting device, photo sensor, modulator, solar cell and integrated circuit.    ADVANTAGE - The oxygen gettering layer is formed of the material with desirable interfacial characteristics after oxidization and compact layer characteristics, thus preventing oxygen from penetrating into the compound semiconductor layer and preventing mutual diffusion of elements between the compound semiconductor layer and the dielectric layer, and hence improving an interfacial characteristic of the compound semiconductor layer. The device utilizes a small subthreshold swing to realize high Ion/Ioff ratio, so that a deterioration of a capacitance characteristic in an accumulation region of a MOS capacitor is reduced or prevented, and the deterioration of carrier mobility at an interface is reduced or prevented, thus improving a driving speed and decreasing an off leakage current, and hence reducing power consumption.    DETAILED DESCRIPTION - The oxygen gettering layer comprises one of a transition metal, a doped zirconium, a lanthanum-based metal, a metal sulfide and a metal nitride. The doped zirconium comprises one of yttrium-doped zirconium and aluminum-doped zirconium. The passivation layer comprises one of sulfur, nitrogen, fluorine, chlorine and hydrogen formed on a surface of the compound semiconductor layer. The compound semiconductor layer includes Group III element selected from gallium and indium, group V element selected from arsenic and phosphorus and a chalcogenide group VI element. An INDEPENDENT CLAIM is also included for a method for fabricating a semiconductor device.    DESCRIPTION OF DRAWING(S) - The drawing shows a cross sectional view of a compound semiconductor device.    Compound semiconductor device (10)    Compound semiconductor layer (11)    Oxygen gettering layer (12)    Dielectric layer (13)    Electrode (14)