Memory elements, switching elements, and peripheral circuits to constitute a nonvolatile memory are integrally formed on a substrate by using TFTs. Since semiconductor active layers of memory element TFTs are thinner than those of other TFTs, impact ionization easily occurs in channel regions of the memory element TFTs. This enables low-voltage write/erase operations to be performed on the memory elements, and hence the memory elements are less prone to deteriorate. Therefore, a nonvolatile memory capable of miniaturization can be provided.