A method for the passivation of a semiconductor substrate, wherein a SiN_x:H layer is deposited on the surface of the substrate (1) by means of a PECVD process comprising the following steps:

• the substrate (1) is placed in a processing chamber (5) which has specific internal processing chamber dimensions;
• the pressure in the processing chamber is maintained at a relatively low value;
• the substrate (1) is maintained at a specific treatment temperature;
• a plasma (P) is generated by at least one plasma cascade source (3) mounted on the processing chamber (5) at a specific distance (L) from the substrate surface;
• at least a part of the plasma (P) generated by each source (3) is brought into contact with the substrate surface; and
• flows of silane and ammonia are supplied to said part of the plasma (P).