The objective of the proposed research is to demonstrate the novel heterogeneous photonic platforms for ultra-fast and low-power active photonic devices, which are urgently needed for communication/interconnection links and computing engines. I will first introduce a heterogeneous integration of the conventional CMOS-compatible material Si3N4 and the emerging electro-optic (EO) material lithium niobate (LiNbO3, LN), which aims to form an electro-optically active, ultra-low-loss, ultra-fast, and reconfigurable Si3N4-on-LNOI platform. In addition to the complete development of the material platform and fabrication processes, the EO-active devices are demonstrated on the heterogeneous platform, including the phase shifter, coupling modulator, and photonic crystal microring resonators (PhCR). Another complementary-metal-oxide-semiconductor (CMOS) photonic platform enabled by commercial foundries will then be introduced, which achieves large scalability and high energy efficiency with monolithic electro-photonic integration. Devices demonstration includes a microring-based transceiver as well as a cascaded microring transceiver tuned by the polysilicon heater. The heterogeneous integration is proven to bring various functionalities together to harness the best-suited properties, which is now widely applied in advanced photonics.