A semiconductor device includes a landing pad on a substrate, a lower electrode on the landing pad, the lower electrode including an outer protective layer, a conductive layer between opposing sidewalls of the outer protective layer, and an inner protective layer between opposing sidewalls of the conductive layer, a first supporter pattern on a side surface of the lower electrode, the first supporter pattern including a supporter hole, a dielectric layer on a surface of each of the lower electrode and the first supporter pattern, and an upper electrode on the dielectric layer. The outer protective layer includes titanium oxide, the conductive layer includes titanium nitride, and the inner protective layer includes titanium silicon nitride. In a horizontal cross-sectional view, the outer protective layer has an arc shape that extends between the dielectric layer and the conductive layer.