Patent ID: 8692372

Claim:
A semiconductor device comprising: a semiconductor substrate; an insulating layer that includes a contact hole through which the semiconductor substrate is exposed; and a polysilicon layer that is configured to fill and cover the contact hole, the polysilicon layer comprising: a first polysilicon layer formed in the contact hole and that is doped with impurities; an impurity-diffusion prevention layer that is formed on the first polysilicon layer in the contact hole; and a second polysilicon layer that is formed on the impurity-diffusion layer, that is doped with impurities and that is configured to fill and cover the contact hole, wherein the impurity-diffusion prevention layer is configured to prevent impurities included in the second polysilicon layer from diffusing into the insulating layer and into the semiconductor substrate, and wherein the impurity diffusion prevention layer comprises at least one diffusion-prevention impurity material selected from a group including carbon and oxygen.