We present first investigations of the electrical characteristics of high-k amorphous BaO, SrO and crystalline Ba0.7Sr0.30 films on n-Si(001). The MOS structures were grown in a UHV chamber on structured SiO2 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 SiO2) achieved so far in BaO, SrO and Ba0.7Sr0.30 MOS-diodes were 1.0, 3.5 and 1.6 nm at oxide thicknesses of 5, 10 and 10 nm, respectively. The corresponding leakage current densities at + 1 V accumulation bias were 2.1, 1.3.10(-5) and 4.7.10(-6)A/cm(2). The lowest interface trap densities observed at similar to 0.2 eV below the conduction band in MOS-diodes with BaO, SrO and Ba0.7Sr0.3O 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. (C) 2009 Elsevier B.V. All rights reserved.