Disclosed are semiconductor memory devices and methods of fabricating the same. The semiconductor memory devices may include a capacitor including first and second electrodes and a dielectric layer. The dielectric layer may include a zirconium aluminum oxide layer including a first zirconium region adjacent to the first electrode, a first aluminum region, a second aluminum region adjacent to the second electrode, and a second zirconium region between the first and second aluminum regions. The first and second zirconium regions may include zirconium and oxygen and may be devoid of aluminum. The first and second aluminum regions may include aluminum and oxygen and may be devoid of zirconium. The first aluminum region and the first zirconium region may be spaced apart by a first distance, and the first aluminum region and the second zirconium region may be spaced apart by a second distance shorter than the first distance.