Semiconductor memory devices and methods of forming the same

Methods of forming semiconductor devices may be provided. A method of forming a semiconductor device may include patterning first and second material layers to form a first through region exposing a substrate. The method may include forming a first semiconductor layer in the first through region on the substrate and on sidewalls of the first and second material layers. In some embodiments, the method may include forming a buried layer filling the first through region on the first semiconductor layer. In some embodiments, the method may include removing a portion of the buried layer to form a second through region between the sidewalls of the first and second material layers. Moreover, the method may include forming a second semiconductor layer in the second through region.