We developed silicon oxynitride (SiON) waveguides and branches working at around 850 nm wavelength for on-chip optical interconnection. SiON films were deposited by plasma-enhanced chemical vapor deposition (PECVD) and were very transmissive in this wavelength region. The propagation losses of fabricated waveguides were as low as 0.2-0.3 dB/cm. The branches are based on multimode interference (MMI) and exhibited excellent 3 dB characteristics. We also integrated a SiON waveguide with a Si nano-photodiode (PD) with a surface plasmon antenna. A large photocurrent of about 0.1 mA at a coupling length of only 10 mu m and a high-speed response of 17 ps were demonstrated for the waveguide-integrated Si nano-PD.