An electronic device includes a semiconductor memory. A method for fabricating the electronic device includes forming a first memory cell extending vertically from a surface of substrate and having a first upper portion that protrudes laterally, forming a second memory cell extending vertically from the surface of the substrate and having a second upper portion that protrudes laterally towards the first upper portion, and forming a liner layer over the first and second memory cells, the liner layer having a first portion disposed over the first upper portion and a second portion disposed over the second upper portion, the first and second portions of the liner layer contacting each other.