1. Field of the Invention
The present invention relates to a fabrication method of a semiconductor device.
2. Description of the Related Art
A silicon oxide film has been used as a gate insulating film or the like in field effect transistors in a semiconductor integrated circuit (IC). Silicon oxide is an extremely excellent material for an insulating film because silicon oxide has a relatively high endurance voltage and a relatively low leakage current level. On the other hand, the silicon oxide film has a relatively low dielectric constant, which may be disadvantageous for recent further miniaturization and higher integration of ICs.
Along with a recent demand for higher integration of ICs, use of a high-k film having a higher dielectric constant than the silicon oxide film has been considered as the gate insulating film or the like.
Such a high-k film may be formed by a Chemical Vapor Deposition (CVD) method or an Atomic Layer Deposition (ALD) method, and then a thermal treatment is carried out with respect to the deposited high-k film in order to reduce residual impurities therein.
However, the thermal treatment may have a problem that the high-k film becomes poly-crystalline, which leads to increased leakage current.    Patent Document 1: Examined Patent Publication No. H03-067346