<p>Electronic ceramic substrates (ECS), as core functional carriers in integrated circuit packaging, directly influence the integration level, power density, and long-term reliability of modern electronic systems. Their applications have expanded from traditional microelectronic packaging to areas including power electronics, optoelectronics, RF/microwave communication, biosensing, civil engineering (bridge health monitoring), and aerospace. This review systematically addresses three main themes: fabrication mechanisms, performance optimization, and integration applications. Beginning with microscopic mechanisms, it discusses the critical roles of organic additives in enhancing slurry dispersibility, improving green tape flexibility, and suppressing defects during tape casting. The effects of sintering additives on crystal growth and grain boundary migration are analyzed, along with the influence of sintering processes on densification and microstructural evolution. Subsequently, the review summarizes recent advances in mainstream ECS—including alumina-based, aluminum nitride-based, silicon nitride-based, and zirconia-toughened alumina-based—with emphasis on thermal conductivity, mechanical strength, and dielectric properties. Corresponding advanced forming and sintering techniques are also discussed. Finally, the engineering practices of ECS in these application scenarios are examined. Looking forward, driven by wide-bandgap semiconductors and high-density integration, high-performance ECS are evolving from passive carriers toward functional integration, a trend that will shape the future architecture of advanced packaging systems.</p>