An interconnection structure includes an underlying layer including a lower interconnection, and an interlayered dielectric layer including a contact hole and a trench therein. The contact hole exposes a portion of the lower interconnection, and the trench extends along a first direction to be connected to the contact hole. A contact plug extends through the contact hole in the interlayered dielectric layer, and an upper interconnection line extends in the trench of the interlayered dielectric layer and connects to the contact plug. The contact plug includes lower and upper sidewalls inclined at first and second angles, respectively, relative to the underlying layer, and the second angle is less than the first angle. Related devices and fabrication methods are also discussed.