A memory device includes a substrate having a first source film thereon and an upper stacked structure on the first source film. An electrically conductive channel structure is provided, which extends through the upper stacked structure and the first source film. The channel structure includes a channel pattern, which extends vertically through the upper stacked structure and the first source film, and an information storage pattern on a sidewall of the channel pattern. A second source film is provided, which extends between the first source film and a surface of the substrate. The second source film, which contacts the channel pattern, includes an upward extending protrusion, which extends underneath the information storage pattern. A channel protective film is provided, which extends between at least a portion of the protrusion and at least a portion of the information storage pattern.