Methods of forming memory devices are provided. The methods may include forming a pre-stacked gate structure including a lower structure and a first polysilicon pattern on the substrate. The methods may also include forming an insulation layer covering the pre-stacked gate structure. The methods may further include forming a trench in the insulation layer by removing a portion of the first polysilicon pattern. The methods may additionally include forming a metal film pattern in the trench on the first polysilicon pattern. The methods may also include forming a first metal silicide pattern by performing a first thermal treatment on the first polysilicon pattern and the metal film pattern. The methods may further include forming a second polysilicon pattern in the trench. The methods may additionally include forming a second metal silicide pattern by performing a second thermal treatment on the second polysilicon pattern and the first metal silicide pattern.