The structural characteristics of Au-TiB2/GaAs and Au-Mo-TiB2-AuGe/GaAs device structures after deposition and short-term thermal annealing (STTA) were investigated. The multilayer contacts with TiB2 anti-diffusion layer were magnetron sputtered on (001) GaAs substrates. The structures were STTA in a stream of hydrogen at temperatures of 400degreesC, 600degreesC, and 800degreesC during 60 seconds. The X-ray diffraction techniques and atomic force microscopy were used for investigation. At STTA a reduction of residual strain in multilayer metallic films, an increment of film grain size, a change of grains preferred orientation in the Au polycrystalline film and a transformation of surface morphology of the upper Au film were observed. These processes do not have monotonic temperature dependence. For Au-TiB2/GaAs a minimum value of residual strains was observed at T=600degreesC while for Au-Mo-TiB2-AuGe/GaAs it was observed at T=400degreesC. The roughness of Au film monotonically increased at annealing of Au-TiB2/GaAs structure at T=400degreesC and T=600degreesC and corresponded to the initial value at T=800degreesC. A strong change of Au film roughness was observed at annealing of Au-Mo-TiB2-AuGe/GaAs structure at T=600degreesC. The XRD pattern from a Au-TiB2 metal film denoted a quasi-amorphous structure in the initial state and an increment of micrograms size at STTA. In the initial state the crystalline structure of Au film in Au-Mo-TiB2-AuGe/GaAs structure had some preferred orientation in the <111> direction, which was reduced after STTA at T=600degreesC. The polycrystalline structure of Au film was partially deteriorated after STTA at T=800degreesC as TiB2 layer was destroyed and lost its diffusion protecting properties.