Semiconductor memory devices and methods of fabricating the semiconductor memory devices are provided, the semiconductor memory devices may include a one-time-programmable (OTP) cell and an electrically erasable programmable read-only memory (EEPROM). The OTP cell includes a memory transistor and a program transistor. The program transistor may include a fuse electrode and may be spaced apart from the memory transistor. The EEPROM cell includes a memory transistor including a first gate and a selection transistor including a second gate. The OTP cell includes a first high-density impurity region which overlaps with the fuse electrode.