A semiconductor device includes memory strings each including a drain select transistor, memory cells and a source select transistor, which are connected between a bit line and a common source line and suitable for operating based on voltages applied to a drain select line, word lines and a source select line, respectively, and an operation circuit suitable for performing a pre-program operation, an erase operation and a post-program operation on the memory strings. The operation circuit sequentially performs erase operations on the drain select transistors included in the memory strings.