A semiconductor device structure is provided. The structure includes a semiconductor substrate and a lower electrode over the semiconductor substrate. The structure also includes a resistance variable layer over the lower electrode and an ion diffusion barrier layer over the resistance variable layer. The structure further includes a capping layer over the ion diffusion barrier layer, and the capping layer is made of a metal material. In addition, the structure includes an upper electrode over the capping layer. The structure includes a protective element extending along a sidewall of the ion diffusion barrier layer and in direct contact with an interface between the resistance variable layer and the ion diffusion barrier layer.