A semiconductor device includes a low-density substrate, a high-density patch positioned inside a cavity in the low-density substrate, a first semiconductor die, and a second semiconductor die. The first semiconductor dies includes high-density bumps and low-density bumps. The second semiconductor die includes high-density bumps and low-density bumps. The high-density bumps of the first semiconductor die and the high-density bumps of the second semiconductor die are electrically connected to the high-density patch. The low-density bumps of the first semiconductor die and the low-density bumps of the second semiconductor die are electrically connected to the low-density substrate.