A foundry-compatible platform for monolithic back-end-of-line integration of phase change materials (PCMs) into silicon photonics is demonstrated, enabling the integration of nonvolatile materials without modifying existing photonic component libraries. The integration involves a silicon nitride (SiN) etch stop layer and low-loss oxide trenches, allowing the incorporation of two chalcogenide PCMs, Sb₂Se₃ and Ge₂Sb₂Se₄Te₁ (GSS4T1), into silicon photonics. These materials offer compact phase and intensity tuning units with zero static power consumption. The integration reduces the peak power consumption of a push-pull Mach-Zehnder interferometer (MZI) optical switch by 48% and enables micro-ring filters with >5-bit wavelength selective intensity modulation and waveguide-based >7-bit intensity modulation broadband attenuators. The platform supports large-scale integration of nonvolatile reconfigurable optoelectronic chips. The integration of PCMs into silicon photonics is crucial for reducing power consumption and enabling advanced photonic applications such as optical communication, microwave photonics, and optical quantum computing. The study demonstrates the feasibility of integrating PCMs into silicon photonic processes, paving the way for future silicon photonic design kits. The integration process involves customizing the silicon photonic process flow, introducing a SiN etch stop layer, and etching deep SiO₂ trenches for PCM integration. The results show that the integration enables nonvolatile phase modulation, intensity modulation, and reconfigurable photonic circuits with high performance and low power consumption. The study highlights the potential of PCMs for future silicon photonic applications and provides a clear path for integrating other optoelectronic materials into silicon photonic processes.A foundry-compatible platform for monolithic back-end-of-line integration of phase change materials (PCMs) into silicon photonics is demonstrated, enabling the integration of nonvolatile materials without modifying existing photonic component libraries. The integration involves a silicon nitride (SiN) etch stop layer and low-loss oxide trenches, allowing the incorporation of two chalcogenide PCMs, Sb₂Se₃ and Ge₂Sb₂Se₄Te₁ (GSS4T1), into silicon photonics. These materials offer compact phase and intensity tuning units with zero static power consumption. The integration reduces the peak power consumption of a push-pull Mach-Zehnder interferometer (MZI) optical switch by 48% and enables micro-ring filters with >5-bit wavelength selective intensity modulation and waveguide-based >7-bit intensity modulation broadband attenuators. The platform supports large-scale integration of nonvolatile reconfigurable optoelectronic chips. The integration of PCMs into silicon photonics is crucial for reducing power consumption and enabling advanced photonic applications such as optical communication, microwave photonics, and optical quantum computing. The study demonstrates the feasibility of integrating PCMs into silicon photonic processes, paving the way for future silicon photonic design kits. The integration process involves customizing the silicon photonic process flow, introducing a SiN etch stop layer, and etching deep SiO₂ trenches for PCM integration. The results show that the integration enables nonvolatile phase modulation, intensity modulation, and reconfigurable photonic circuits with high performance and low power consumption. The study highlights the potential of PCMs for future silicon photonic applications and provides a clear path for integrating other optoelectronic materials into silicon photonic processes.