A method provides electrical connections to a stack of contact levels of an interconnect region for a 3-D stacked IC device. Each contact level comprises conductive and insulation
layers. A portion of any upper layer is removed to
expose a first contact level and create contact openings for each contact level. A set of N masks is used to etch the contact openings up to and including 2N contact levels. Each
mask is used to etch effectively half of the contact openings. When N is 3, a first
mask etches one contact level, a second
mask etches two contact levels, and a third mask etches four contact levels. A
dielectric layer may be formed on the sidewalls of the contact openings. Electrical conductors may be formed through the contact openings with the
dielectric layers electrically insulating the electrical conductors from the sidewalls.