PURPOSE: To provide a method and a system for depositing a silicon dioxide based dielectric film under low temperature at a fine and significant level difference part having high aspect ratio with good step coverage and no void using ECR plasma CVD.

CONSTITUTION: ECR plasma CVD is employed while using silicon tetrafluoride and nitrogen suboxide containing or not containing phosphine as reaction gas. Silicon tetrafluoride is reacted on polysilicon particles 20 in an intermediate production chamber 19 to produce silicon difluoride which is introduced, as reaction gas, into a reaction chamber 2. The dielectric film deposition system comprises a microwave oscillator 3, a magnet coil 7, and a plasma generating gas introduction pipe 6 arranged in a plasma generating chamber 1, a silicon difluoride gas introduction pipe and an evacuation pipe 5 arranged in the reaction chamber 2, an XeCl excimer laser source 23 for irradiating the inside of reaction chamber, a permanent magnet 24 and a scanning mechanism 25 arranged at the lower part of the reaction chamber 2.