Method for fabricating a cylindrical capacitor including implanting impurities into the upper sections of the lower electrode to prevent the formation of hemispherical grain silicon on the upper sections

1. A method for fabricating a semiconducter device, the semiconductor device including a capacitor and a support insulator, the capacitor including a cylindrical electrode, the cylindrical electrode extending in a vertical direction, the method comprising:

forming the cylindrical electrode, the cylindrical electrode comprising upper and lower sections, the lower section having a supported outer surface supported by the support insulator and a roughened inner surface, the upper section upwardly projecting from the support insulator and having an exposed outer surface, the forming of the cylindrical electrode comprising:

forming an initial cylindrical electrode supported by the support insulator, the initial cylindrical electrode comprising an initial upper section and an initial lower section, the initial upper section and the initial lower section corresponding to the upper section and the lower section of the cylindrical electrode, respectively, the initial upper section being supported by the support insulator;

implanting specific impurities into the initial upper section, the specific impurities serving to prevent the initial upper section from being roughened;

exposing the initial cylindrical electrode to a roughening process so that the initial lower section is roughened to be the lower section,

forming a first insulator;

forming a second insulator on the first insulator;

etching the first and the second insulators to form a hole that extends in the first and the second insulators along the vertical direction and has an inner surface, wherein the forming of the initial cylindrical electrode is carried out so that the initial cylindrical electrode is formed on the inner surface of the hole, while etched first insulator constitutes the support insulator; and

removing the second insulator before the implanting, and the implanting is carried out so that the specific impurities are implanted into outer and inner surfaces of the initial upper section along a direction oblique to the vertical direction.

2. The method to claim 1 wherein the etching is carried out by using a specific etchant, the first insulator having a first etching rate with respect to the specific etchant, and the second insulator having a second etching rate smaller than the first etching rate with respect to the specific etchant.

3. The method according to claim 1 further comprising forming a film that covers, at least in part, the cylindrical electrode, the film comprising metal elements.

4. The method according to claim 1 wherein:

the forming of the initial cylindrical electrode is carried out so that the initial cylindrical electrode is made of amorphous silicon;

the implanting is carried out so that phosphorus elements are implanted as the specific impurities into the initial upper section; and

the exposing is carried out so that the initial lower section is hemispherical grained.