An accurate analytical formula for tunneling probability through the double-layer gate stack is derived. The Wentzel-Krammers-Brillouin approximation equivalent simplification is proposed, too. The derived formulas are used to analyze the tunneling probability of metal-oxide semiconductor structures with the double-layer gate stacks of different parameters and composition. (C) 2009 American Vacuum Society. [DOI: 10.1116/1.3021042]