Semiconductor device and method for manufacturing the same

A semiconductor device comprising a transistor, the transistor comprising:

• a gate electrode over a substrate;
• a gate insulating film over the gate electrode;
• a multilayer film over the gate insulating film;
• a pair of electrodes in electrical contact with the multilayer film;
• a first oxide insulating film over the multilayer film and the pair of electrodes;
• and
• a second oxide insulating film over the first oxide insulating film,
• wherein the multilayer film includes an oxide semiconductor film and an oxide film over the oxide semiconductor film,
• wherein the oxide semiconductor film has an amorphous structure or a microcrystalline structure,
• wherein the first oxide insulating film is an oxide insulating film through which oxygen is permeated,
• wherein the second oxide insulating film is an oxide insulating film containing more oxygen than that in the stoichiometric composition,
• wherein each of the oxide semiconductor film and the oxide film contains In-M-Zn oxide,
• wherein the M represents Al, Ti, Ga, Y, Zr, La, Ce, Nd, or Hf, and
• wherein a proportion of M atoms in the oxide film is higher than a proportion of M atoms in the oxide semiconductor film.

A method for manufacturing a semiconductor device, comprising the steps of:

• forming a gate electrode over a substrate;
• forming a gate insulating film over the gate electrode;
• forming a multilayer film including an oxide semiconductor film having an amorphous structure or a microcrystalline structure and an oxide film containing at least one of In and Ga, over the gate insulating film;
• forming a pair of electrodes in electrical contact with the multilayer film;
• forming a first oxide insulating film over the multilayer film and the pair of electrodes;
• and
• forming a second oxide insulating film over the first oxide insulating film,
• wherein the step of forming the first oxide insulating film comprises the steps of:
• placing the substrate in a treatment chamber which is vacuum-evacuated and held at temperatures higher than or equal to 180 ° C. and lower than or equal to 400 ° C.;
• and
• setting a pressure in the treatment chamber to be greater than or equal to 20 Pa and less than or equal to 250 Pa with introduction of a first source gas into the treatment chamber, and
• wherein the step of forming the second oxide insulating film comprises the steps of:
• placing the substrate in a treatment chamber which is vacuum-evacuated and held at temperatures higher than or equal to 180 ° C. and lower than or equal to 260 ° C.;
• setting a pressure in the treatment chamber to be greater than or equal to 100 Pa and less than or equal to 250 Pa with introduction of a second source gas into the treatment chamber;
• and
• supplying a frequency power higher than or equal to 0.17 W/cm2 and lower than or equal to 0.5 W/cm2 to an electrode provided in the treatment chamber.