Semiconductor device and method for fabricating the same

1. A semiconductor device comprising:

a first conductive type semiconductor substrate having an active region and a field region defined thereon, and a trench formed in the field region;

a storage dielectric film on an inside surface of the trench;

a first storage electrode of a capacitor in the trench having the dielectric film formed therein;

a protective film on the first storage electrode;

a second conductive type epitaxial layer on an entire surface of the first conductive type semiconductor substrate;

an active cell isolation film in the field region of the second conductive type epitaxial layer;

a transistor on the second conductive type epitaxial layer in the active region, the transistor having a source and/or drain region;

an open trench formed by selectively removing the second conductive type epitaxial layer adjacent to the active cell isolation film and the protective film; and

a second storage electrode in the open trench configured to connect the source and/or drain region of the transistor and the first storage electrode.

2. The semiconductor device as claimed in claim 1 , wherein the second storage electrode is electrically isolated from the semiconductor substrate.

3. The semiconductor device as claimed in claim 1 , wherein the storage dielectric film has a thickness ranging from about 100 Å to about 1000 Å.

4. The semiconductor device as claimed in claim 1 , wherein the second conductive type epitaxial layer has a thickness ranging from about 3000 Å to about 8000 Å.

5. A method for fabricating a semiconductor device, comprising the steps of:

forming a trench in a field region of a first conductive type semiconductor substrate, the first conductive type semiconductor substrate having an active region and the field region defined thereon;

forming a storage dielectric film on an inside surface of the trench;

forming a first storage electrode in the trench;

forming a protective film on the first storage electrode;

forming a second conductive type epitaxial layer on an entire surface of the first conductive type semiconductor substrate;

forming an active cell isolation trench in the second conductive type epitaxial layer in the field region;

forming an active cell isolation film in the active cell isolation trench;

forming an open trench in the second conductive type epitaxial layer adjacent to the active cell isolation film to expose the first storage electrode;

forming a second storage electrode in the open trench, the second storage electrode connected to the first storage electrode; and

forming a transistor on the second conductive type epitaxial layer in the active region such that a source and/or drain region is connected to the second storage electrode.

6. The method as claimed in claim 5 , wherein the step of forming a storage dielectric film includes forming the storage dielectric film of an oxide film.

7. The method as claimed in claim 5 , wherein the step of forming a storage dielectric film includes forming the storage dielectric film with a thickness ranging from about 100 Å to about 1000 Å.

8. The method as claimed in claim 5 , wherein the step of forming a second conductive type epitaxial layer includes forming the second conductive type epitaxial layer with a thickness ranging from about 3000 Å to about 8000 Å.

9. The method as claimed in claim 5 , wherein the step of forming a second conductive type epitaxial layer includes forming the second conductive type epitaxial by depositing a single crystal silicon layer.