Semiconductor devices having improved heat dissipation and methods of forming the same are disclosed. In an embodiment, a device includes a first transistor structure; a front-side interconnect structure on a front-side of the first transistor structure, the front-side interconnect structure including front-side conductive lines; a backside interconnect structure on a backside of the first transistor structure, the backside interconnect structure including backside conductive lines, the backside conductive lines having line widths greater than line widths of the front-side conductive lines; and a first heat dissipation substrate coupled to the backside interconnect structure.