Abstract Recent demand and initiatives in brain research have driven significant interest towards developing chronically implantable neural interface systems with high spatiotemporal resolution and spatial coverage extending to the whole brain. Electroencephalography-based systems are noninvasive and cost-efficient in monitoring neural activity across the brain, but suffer from fundamental limitations in spatiotemporal resolution. On the other hand, neural spike and local field potential (LFP) monitoring with penetrating electrodes offer higher resolution, but are highly invasive and inadequate for long-term use in humans due to unreliability in long-term data recording and risk for infection and inflammation. Alternatively, electrocorticography (ECoG) promises a minimally invasive, chronically implantable neural interface with resolution and spatial coverage capabilities that, with future technology scaling, may meet the needs of recently proposed brain initiatives. This chapter discusses current challenges of current ECoG technologies on electrodes, data acquisition front-ends, stimulation, wireless communications, power delivery and encapsulation In addition, we introduce two representative approaches that are enabling next-generation fully implantable high-density ECoG interfaces, along with an overview of this book.