Silicon nitride (SiN) films were deposited by a newly-proposed mirror-plasma enhanced chemical vapor deposition (MPECVD) method using SiH4 and N2 based plasmas. MPECVD method utilizes the magnetic-mirror confined electron cyclotron resonance plasma source to realize low ion-bombardment damage plasma processings. The deposition temperature ranged from room temperature to 400°C in the experiment. The SiN films having excellent wet etching resistance against HF solution could be obtained. In addition, the conformal SiN-film deposition on the Si trench pattern was confirmed with mostly keeping the wet etching resistance against HF solution for all the regions of the top, the sidewall and the bottom surface. Both the conformality and the wet etching resistance against HF solution of the SiN film on the trench pattern were better than the case of the conventional PECVD.