The present disclosure provides a semiconductor structure. The semiconductor structure includes a substrate, a die stack disposed over the substrate, a heat spreader disposed over the substrate and having a surface facing the substrate, and a thermal interface material (TIM) disposed between the die stack and the heat spreader. A bottommost die of the die stack includes a surface exposed from remaining dies of the die stack from a top view perspective; and the TIM is in contact with the exposed surface of the bottommost die and the surface of the heat spreader, and is in contact with a sidewall of at least one of the plurality of dies of the die stack.