u2192 bi u2192 o is repeated one or more times until a sbt layer is formed to a desired thickness the composition ratio of sr bi ta can be varied by further repeating or omitting a sub step of supplying a bismuth source material during one or more cycles of the source material supply thereby resulting in a sbt layer having a desired thickness in embodiments 5a and 5b bi thd 3 biph 3 sr ta oet 6 2 and sr ta oet 5 dmae 2 may be dissolved in a solvent such as thf or n butylacetate and then supplied into the reactor through a liquid source supply unit and a vaporizer in this case the amounts of source materials supplied during each source material supply cycle can be controlled with improved consistency a plasma ald method for forming a pzt layer is disclosed in the present embodiment pb thd 2 is supplied into a reactor and the reactor is purged with ar next oxygen gas is supplied into the reactor to generate plasma and followed by purging with ar next this cycle is repeated with zr o t bu 4 or zr o t bu 2 thd 2 and pb thd 2 finally ti o i pr 4 ti o i pr 2 thd 2 is supplied into the reactor and followed by purging with ar supply of oxygen to generate plasma and purging with ar this cycle of supplying source materials in the sequence of pb u2192 o.