Thin-film transistor and method of fabricating the same

Provided are a thin-film transistor formed by connecting polysilicon layers having different conductivity types with each other which prevents occurrence of inconvenience resulting from diffusion of impurities and a method of fabricating the same. A drain, a channel and a source are integrally formed on a surface of a second oxide film by polysilicon. The drain is formed to be connected with a pad layer (second polycrystalline semiconductor layer) through a contact hole which is formed to reach an upper surface of the pad layer. The pad layer positioned on a bottom portion of the contact hole (opening) is provided with a boron implantation region BR.