Methods of manufacturing semiconductor devices having slopes at lower sides of an interconnection hole include an etch-stop layer and an interlayer dielectric layer sequentially formed on a semiconductor substrate having the lower conductive layer. Portions of the etch-stop layer are exposed by selectively etching the interlayer dielectric layer. A step is formed in the etch-stop layer by removing portions of the exposed etch-stop layer. And, the step is formed at a boundary between a recessed portion of the exposed etch-stop layer and a raised portion of the etch-stop layer covered with the interlayer dielectric layer. Portions of the interlayer dielectric layer are removed to expose portions of the raised portion of the etch-stop layer. And, the exposed recessed and raised portions are anisotropically etched to expose the lower conductive layer and to form the interconnection hole having the slopes, wherein the slopes are made of a residual etch-stop layer at the lower sides of the interconnection hole.