A semiconductor device such as a phase change memory device includes a semiconductor substrate including an active region, a conductive pattern disposed to expose the active region, an interlayer dielectric pattern provided on the conductive pattern and including an opening formed on the exposed active region and a contact hole spaced apart from the opening to expose the conductive pattern, a semiconductor pattern and a heater electrode pattern electrically connected to the exposed active region and provided in the opening, a contact plug connected to the exposed conductive pattern and provided to fill the contact hole, and a phase change material layer provided on the heater electrode pattern.