To achieve high integration and reduction of power of the semiconductor integrated circuit device, the operating voltage of the semiconductor device has been reduced as the generation advances. At this time, to maintain and improve device performance, the MIS transistor has been miniaturized according to the scaling rule and its gate insulation film has been reduced in size. On the other hand, to reduce power consumption, maintain memory information or correspond to an external power supply voltage, a MIS transistor having a relatively thick gate insulation film has been required. For example, because the operating voltage differs between its internal circuit and I/O circuit in case of LSI (large scale integrated circuit) or CMOS (complementary metal oxide semiconductor) logical LSI, plural kinds of MIS transistors whose gate insulation film differs in thickness are formed on the same substrate.
Japanese Patent Application Laid-Open No. 2001-15612 has disclosed a technology that two kinds of silicon oxide films each having a different thickness are formed on the same substrate so as to serve as MIS transistor gate insulation film.
In a MIS transistor whose gate electrode width (hereinafter referred to as gate length) is less than 0.1 μm, it is expected that the thickness of the gate insulation film is less than 1.2 nm. However, if the silicon oxide film, which has been conventionally used as a gate insulation film, is formed in the thickness of less than 1.2 nm, there occurs a problem that leakage current exceeds 10 A/cm2, so that for example standby current increases.
Thus, a trial for reducing an effective thickness with physical film thickness maintained at 2 nm or more has been made by using an insulation film whose dielectric constant is relatively high (hereinafter referred to as high dielectric constant film), for example, alumina film (Al2O3) whose dielectric constant is about 7 as a gate insulation film. The effective thickness means silicon oxide (SiO2) converted film thickness considering dielectric constant.
The present inventors considered a technology for forming two kinds of MIS transistors comprised of each gate insulation film by employing a high dielectric constant insulation film on two kinds of gate insulation films each having a different thickness. The following is the technology considered by the present inventors and it is summarized as below.
First, a first high dielectric constant insulation film is formed on a substrate and after that, the first high dielectric constant insulation film is removed with a resist film as a mask. Next, after the resist film is removed, washing processing is carried out on the substrate and a second high dielectric constant insulation film is formed on the substrate. Consequently, a thin gate insulation film is formed of the second high dielectric constant insulation film in the first region so that a thick gate insulation film is formed of the first and second high dielectric constant insulation films in a second region different from the first region. By forming gate, source, drain and wiring, a MIS transistor having the thin gate insulation film is formed in the first region and a MIS transistor having a thick insulation film is formed in the second region.
However, it is made evident that the fabrication method of the MIS transistor has following problems.
(1) When a difference in level of 20 nm or more is formed between the first region and the second region due to a difference in thickness of the gate insulation film, a trouble occurs in forming step for the gate and forming step for an opening used for passing wiring.
(2) A high selectivity to the substrate and resist film is possessed and new etching technology for a high dielectric constant insulation film free of etching damage and pollution to a substrate needs to be developed.
An object of the present invention is to provide a technology for forming a gate insulation film having a high reliability and at the same time, facilitating manufacturing of a MIS transistor in a semiconductor integrated circuit device containing plural kinds of the MIS transistors each having a different thickness of gate insulation film.
The aforementioned and other objects and novel features of the present invention will be apparent from a description of this specification and accompanying drawings.
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