Method of manufacturing nozzle plate and nozzle plate

A method of manufacturing a nozzle plate having a nozzle and made of a silicon substrate, the method comprising:

• a first nozzle forming step of forming a first nozzle that is open to a first surface of the nozzle plate on one side;
• a second nozzle forming step of forming a second nozzle that is open to a second surface of the nozzle plate on the other side and is connected to the first nozzle;
• a curved portion forming step of forming a first curved portion in a first opening portion of the first nozzle that is open to the first surface, the first curved portion having a rounded shape in which a cross-sectional area gradually increases toward the opening, and a second curved portion having a rounded shape in which a cross-sectional area gradually increases from the first nozzle toward the second nozzle in a connection portion between the first nozzle and the second nozzle by performing an annealing treatment in which the nozzle plate is heated under a hydrogen atmosphere or an argon atmosphere;
• a step of forming a water-repellent film on inner surfaces of the first nozzle and the second nozzle and the first surface;
• and
• a step of removing a part of the water-repellent film by performing a plasma treatment from the second nozzle toward the first nozzle.