Low-noise stable lasers have broad applications in metrology, spectroscopy, communication, and quantum physics. Here we demonstrate locking a semiconductor laser to an on-chip silicon nitride Mach-Zehnder interferometer (MZI) using the Pound-Drever-Hall (PDH) stabilization technology. After locking, the frequency noise of the laser is suppressed by up to 37 dB, and the relative stability reaches 3