Vapor deposition reactor and method for forming thin film

A vapor deposition reactor comprising:

• a first portion of a body formed with a first recess for receiving a reaction material, the first portion of the body having a first bottom surface defining the first recess and facing a substrate passing below the vapor deposition reactor, the first recess subject to a first pressure of the reaction material and formed within the first portion at a lower side of the body;
• a second portion of the body adjacent to the first portion of the body, the second portion formed with a second recess communicatively connected to the first recess, the second portion of the body having a second bottom surface defining the second recess and facing the substrate, the second recess subject to a second pressure of the reaction material lower than the first pressure by having a height not greater than ⅔ of a width of the first recess, the height representing a vertical distance between a lowest surface of the body and the second bottom surface;
• and
• a third portion of the body adjacent to the second portion of the body, the third portion communicatively connected to the second portion of the body to discharge the reaction material from the vapor deposition reactor, the second portion bounded at sides by the first and third portions.