A semiconductor device includes a substrate having a first conductive type. An epitaxial layer having a second conductive type is disposed on the substrate. A first buried layer of the second conductive type is disposed within a high side region of the substrate. A second buried layer of the second conductive type is disposed directly above the first buried layer of the second conductive type. A top surface of the first buried layer of the second conductive type and a top surface of the second buried layer of the second conductive type are apart from a top surface of the epitaxial layer by different distances. A dopant concentration of the first buried layer of the second conductive type is less than that of the second buried layer of the second conductive type.