PURPOSE: To form a uniform thin ZnO film at low temp. by giving microwave energy to Zn or Zn compound to evaporate the same, allowing the evaporating gas to react in a plasma atmosphere and vapordepositing the product formed by this on substrates.

CONSTITUTION: Substrates 1 are erected on a quartz boat 2 in a reaction furnace 3, and a departing material 4 such as Zn, ZnO or a Zn compound is disposed in a boat 5, and is heated in an electric furnace 10. Hydrogen, inert gas and gaseous oxide 14, 15, 16 activated by microwave energy are introduced into the furnace 3 through flowmeters 17, 18, 19, thereby evaporating the material 4. On the other hand, high frequency energy is applied between electrodes 6 and 7 from a generating source 8 to generate plasma discharge in the entire part of the furnace 3. Therefore, the evaporating gas reacts to form ZnO, which is vapor-deposited on the surface of the substrates 1.