Stress controllable silicon nitride(Si Nx) films deposited by plasma enhanced chemical vapor deposition(PECVD) are reported. Low stress Si Nx films were deposited in both high frequency(HF) mode and dual frequency(HF/LF) mode. By optimizing process parameters, stress free(-0.27 MPa) Si Nx films were obtained with the deposition rate of 45.5 nm/min and the refractive index of 2.06. Furthermore, at HF/LF mode, the stress is significantly influenced by LF ratio and LF power, and can be controlled to be 10 MPa with the LF ratio of 17% and LF power of 150 W. However, LF power has a little effect on the deposition rate due to the interaction between HF power and LF power. The deposited Si Nx films have good mechanical and optical properties, low deposition temperature and controllable stress, and can be widely used in integrated circuit(IC), micro-electro-mechanical systems(MEMS) and bio-MEMS. Stress controlledlable silicon nitride (Si Nx) films deposited by plasma enhanced chemical vapor deposition (PECVD) are reported. Low stress Si Nx films were deposited in both high frequency (HF) mode and dual frequency (HF / LF) mode. At, HF / LF mode, the stress is significantly affected by LF ratio and LF power, and the stress free (-0.27 MPa) Si Nx films were obtained with the deposition rate of 45.5 nm / min and the refractive index of 2.06. and LF can be controlled to 10 MPa with the LF ratio of 17% and LF power of 150 W. However, LF power has a little effect on the deposition rate due to the interaction between HF power and LF power. The deposited Si Nx films have good mechanical and optical properties, low deposition temperature and controllable stress, and can be widely used in integrated circuits (ICs), micro-electro-mechanical systems (MEMS) and bio-MEMS.