Ge-based NMOS device and method for fabricating the same
The embodiments of the present invention provide a Ge-based NMOS device structure and a method for fabricating the same. By using the method, double dielectric layers of germanium oxide (GeO 2 ) and metal oxide are deposited between the source/drain region and the substrate. The present invention not only reduces the electron Schottky barrier height of metal/Ge contact, but also improves the current switching ratio of the Ge-based Schottky and therefore, it will improve the performance of the Ge-based Schottky NMOS transistor. In addition, the fabrication process is very easy and completely compatible with the silicon CMOS process. As compared with conventional fabrication method, the Ge-based NMOS device structure and the fabrication method in the present invention can easily and effectively improve the performance of the Ge-based Schottky NMOS transistor.
1. A Ge-based Schottky NMOS transistor, wherein, a germanium oxide layer and a metal oxide layer are deposited between a substrate and a source/drain region by depositing the germanium oxide layer over the substrate, depositing a metal oxide layer over the germanium oxide layer, and a metal source/drain is located over the metal oxide layer, wherein a ratio between the areal density of oxygen of metal oxide and that of GeO 2 is less than 0.8.
2. The Ge-based Schottky NMOS transistor according to claim 1 , wherein, the germanium oxide layer has a thickness of 0.5˜4 nm.
3. The Ge-based Schottky NMOS transistor according to claim 1 , wherein, the metal oxide layer has a thickness of 0.5˜4 nm.
4. The Ge-based Schottky NMOS transistor according to claim 1 , wherein, the metal oxide is selected from strontium oxide, barium oxide or radium oxide.
5. A method for fabricating a Ge-based Schottky NMOS transistor, comprising the following steps:
1-1) fabricating a MOS structure over a Ge-based substrate;
1-2) depositing a GeO 2 layer and a metal oxide layer in a source/drain region;
1-3) sputtering a metal film with low work function, etching the metal film to form the metal source/drain; and
1-4) forming a contact hole and a metal line, wherein a ratio between the areal density of oxygen of metal oxide and that of GeO 2 is less than 0.8.
6. The method according to claim 5 , wherein, the step 1-1) comprises:
2-1) fabricating an isolation region over the substrate;
2-2) depositing a gate dielectric layer and forming a gate;
2-3) forming a gate structure; and
2-4) forming a sidewall structure.
7. The method according to claim 5 , wherein, the Ge-based substrate in the step 1-1) comprises a bulk Ge substrate, a Ge-on-insulator substrate or an epitaxial Ge substrate.
8. The method according to claim 5 , wherein the metal oxide is selected from strontium oxide, barium oxide, or radium oxide.
9. The method according to claim 5 , wherein, the metal film in the step 1-3) is an aluminum film or other metal film with low work function.