Method of manufacturing a semiconductor device, and a semiconductor substrate

1. A method of manufacturing a semiconductor device, comprising:

forming a thin film on a major surface of a Si substrate, the major surface having face orientation ( 100 );

removing a part of the thin film which lies on an element-isolating region; and

selectively etching the Si substrate by using the thin film as a mask and applying a mixture solution containing hydrofluoric acid and ozone water to the Si substrate,

wherein the Si substrate undergoes selective anisotropic etching until a ( 110 ) face is exposed at sides of the Si substrate, thereby forming an element-isolating trench in the Si substrate having no side-etched parts.

2. The method according to claim 1 , wherein the thin film is an oxide film formed by thermally oxidizing the Si substrate.

3. The method according to claim 2 , wherein the oxide film is etched at a rate lower than the Si substrate when the Si substrate is etched, and has such a thickness as to be etched away when etching of the Si substrate is completed.

4. The method according to claim 1 , wherein hydrofluoric acid and ozone water have concentration of 0.05 to 2 wt % and concentration of 3 to 20 ppm, respectively, in the mixture solution.

5. The method according to claim 1 , wherein a resist pattern is formed on the thin film in order to remove that part of the thin film which lies on an element-isolating region, selective etching is performed on the thin film by using the resist pattern as mask, and the resist pattern is removed after the selective etching is performed.

6. A method of manufacturing a semiconductor device, comprising:

forming a thin film on a major surface of a Si substrate, the major surface having face orientation ( 100 );

removing a part of the thin film which lies on that region of the Si substrate at which an effective major-surface area is to be increased; and

selectively etching the Si substrate by using the thin film as a mask and applying a mixture solution containing hydrofluoric acid and ozone water to the Si substrate,

wherein the Si substrate undergoes selective anisotropic etching until a ( 110 ) face is exposed at sides of the Si substrate, thereby increasing an effective major-surface area of the Si substrate.

7. The method according to claim 6 , wherein the thin film is an oxide film formed by thermally oxidizing the Si substrate.

8. The method according to claim 7 , wherein the oxide film is etched at a rate lower than the Si substrate when the Si substrate is etched, and has such a thickness as to be etched away when etching of the Si substrate is completed.

9. The method according to claim 6 , wherein hydrofluoric acid and ozone water have concentration of 0.05 to 2 wt % and concentration of 3 to 20 ppm, respectively, in the mixture solution.

10. The method according to claim 6 , wherein a resist pattern is formed on the thin film in order to remove that part of the thin film which lies on that part of the Si substrate at which the effective major-surface area is to be increased, selective etching is performed on the thin film by using the resist pattern as mask, and the resist pattern is removed after the selective etching is performed.

11. The method according to claim 6 , wherein the thin film is removed in part, thereby forming a line-opening pattern.

12. The method according to claim 6 , wherein the thin film is removed in part, thereby forming a line-and-space pattern.

13. The method according to claim 6 , further comprising:

forming a capacitor-insulating film on the major surface of the substrate that has the effective major-surface area increased; and forming a capacitor electrode on the capacitor-insulating film.

14. The method according to claim 6 , further comprising: forming a gate-insulating film on the major surface of the substrate that has the effective major-surface area increased; and forming a gate electrode on the gate-insulating film.