A method for forming a polyatomic layer with a mixed deposition method consisting of an atomic layer deposition method (ALD) and a chemical vapor deposition method. The mixed deposition method can be adopted to form a polyatomic high dielectric layer, such as BST or STO. Accordingly, it is possible to form a polyatomic high dielectric layer having a uniform composition distribution, and thereby also having a high dielectric characteristic and a low leakage current characteristic.