本发明描述垂直堆栈式系统级封装结构。在一实施例中，一封装包括一第一层级模制及扇出结构、一第三层级模制及扇出结构，以及在该第一层级与该第三层级之间的一第二层级模制及扇出结构。该第二层级模制及扇出结构包括背对背朝向之晶粒，其中各晶粒之一前表面接合至一重布层。

Vertically stacked system in package structures are described. In an embodiment, a package includes a first level molding and fan out structure, a third level molding and fan out structure, and a second level molding and fan out structure between the first and third levels. The second level molding and fan out structure includes back-to-back facing die, with a front surface of each die bonded to a redistribution layer.