A fabrication method of a self-aligned ferroelectric gate transistor using a buffer layer of high etching selectivity is disclosed. A stacked structure is formed with a buffer layer with high etching selectivity inserted between a silicon substrate and a ferroelectric layer, and etching is performed on a portion where a source and a drain will be formed and then stopped at the buffer layer, thereby fabricating a self-aligned ferroelectric gate transistor without damage to the silicon thin film, and thus, an integration degree of a chip can be improved.