A simple computationally effective semi-analytical macroscopic technique of self-consistent calculations of the electrical properties of the MOS structures with ultra thin high-k gate oxide film is developed. Calculated gate voltage -- gate leakage [substrate-injected direct and Fowler-Nordheim (FN) tunneling] and gate capacitance characteristics are presented and discussed. The Si/oxide band offset is shown to be the main parameter affecting leakage. The stepwise behaviour of the I-V characteristics is predicted. A contribution of the FN injection is discussed.