Semiconductor integrated device and manufacturing method thereof

The invention discloses a semiconductor integrated device and a manufacturing method thereof, and belongs to the technical field of semiconductors, and the semiconductor integrated device comprises a substrate which comprises a flash memory region, a first region and a second region; the plurality of well regions are arranged in the substrate; the gate oxide layer is arranged on the well region; the first gate structure is arranged on the gate oxide layer on the flash memory region and the first region, the first gate structure comprises a first gate layer, an insulating layer and a second gate layer, and the insulating layer is arranged between the first gate layer and the second gate layer; the second gate structure is arranged on the gate oxide layer on the second region, and the second gate structure comprises the second gate layer; and the heavily doped region is positioned in the well region at the two sides of the first gate structure and the second gate structure. According to the semiconductor integr