A semiconductor die assembly is provided. The semiconductor die assembly includes: a first bottom die and a second bottom die disposed at a bottom vertical level; a first top die disposed at a top vertical level above the bottom vertical level in a vertical direction and bonded to the first bottom die; a second top die disposed at the top vertical level and bonded to the second bottom die; and a linking die disposed at the top vertical level and bonded to both the first bottom die and the second bottom die. The linking die is characterized by a polygonal shape in a horizontal plane perpendicular to the vertical direction, and the polygonal shape is not a rectangle.