We present first investigations of the electrical characteristics of high-k amorphous BaO, SrO and crystalline Ba 0.7 Sr 0.3 O films on n-Si(001). The MOS structures were grown in a UHV chamber on structured SiO 2 samples with Si(001) windows and were capped with Au layers afterwards for ex-situ electrical characterization. The smallest capacitance equivalent oxide thicknesses (relative to SiO 2 ) achieved so far in BaO, SrO and Ba 0.7 Sr 0.3 O MOS-diodes were 1.0, 3.5 and 1.6nm at oxide thicknesses of 5, 10 and 10nm, respectively. The corresponding leakage current densities at +1V accumulation bias were 2.1, 1.3·10 −5 and 4.7·10 − 6 A/cm 2 . The lowest interface trap densities observed at ∼0.2eV below the conduction band in MOS-diodes with BaO, SrO and Ba 0.7 Sr 0.3 O films were 5.2·10 12 , 9.7·10 11 and 9.1·10 10 eV −1 cm −2 , respectively. These results suggest that alkaline-earth oxides might be interesting materials for application as high-k gate dielectrics.