A semiconductor device includes: first and second interlayer dielectric films consecutively deposited to overlie a silicon substrate; contact plugs penetrating the first interlayer dielectric film and having a top surface located within the second interlayer dielectric film; and via-plugs having a first portion, the diameter of which reduces from the top of the second interlevel dielectric film toward the bottom thereof and a second portion extending between the first portion and the first plug, the second portion having a diameter increasing from the first portion to the first plug.