Semiconductor devices and methods of forming the semiconductor devices are described herein that are directed towards the formation of a system on integrated substrate (SoIS) package. The SoIS package includes an integrated fan out structure and a device redistribution structure for external connection to a plurality of semiconductor devices. The integrated fan out structure includes a plurality of local interconnect devices that electrically couple two of the semiconductor devices together. In some cases, the local interconnect device may be a silicon bus, a local silicon interconnect, an integrated passive device, an integrated voltage regulator, or the like. The integrated fan out structure may be fabricated in wafer or panel form and then singulated into multiple integrated fan out structures. The SoIS package may also include an interposer connected to the integrated fan out structure for external connection to the SoIS package.