Vertical transistor fabrication for memory applications

Embodiments of the present disclosure provide an apparatus and methods for forming stair-like structures with accurate profiles and dimension control for manufacturing three dimensional (3D) stacked memory cell semiconductor devices. In one embodiment, a memory cell device includes a film stack comprising alternating pairs of dielectric layers and conductive structures horizontally formed on a substrate, an opening formed in the film stack, wherein the opening is filled with a channel layer and a center filling layer, and a protective liner layer disposed between the conductive structure and the channel layer.