Method of fabricating a semiconductor device

A method of fabricating a semiconductor device comprising:

• forming an insulating layer on a semiconductor substrate having a contact hole exposing a portion of the substrate;
• forming on the insulating layer a first conductive layer contacting a predetermined portion of the semiconductor substrate;
• forming on the first conductive layer a first amorphous silicon layer doped with impurity ions at a first impurity density;
• forming on the first amorphous silicon layer a second amorphous silicon layer doped with the impurity ions at a second impurity density higher than the first impurity density;
• forming on the second amorphous silicon layer a third amorphous silicon layer doped with the impurity ions at a third impurity density lower than the first impurity density;
• forming a lower electrode by patterning the first to third amorphous silicon layers and the first conductive layer, wherein the lower electrode comprises the the first to third amorphous silicon layers and the first conductive layer;
• forming hemispherical silicon grains on an exposed surface of the lower electrode;
• forming a dielectric layer on exposed surfaces of the lower electrode and the hemispherical silicon grains;
• and
• forming on the dielectric layer an upper electrode using a second conductive layer.

A method of fabricating a semiconductor device comprising:

• forming an insulating layer on a semiconductor substrate having a contact hole exposing a portion of the substrate;
• forming on the insulating layer a first conductive layer contacting a predetermined portion of the semiconductor substrate;
• patterning the first conductive layer so that the first conductive layer remains in the contact hole and extends on a top surface portion of the insulating layer;
• forming a pillar at a side of the remaining first conductive layers wherein the pillar is constructed using a first amorphous silicon layer doped with impurity ions at a first impurity density, a second amorphous silicon layer doped with impurity ions at a second impurity density higher than the first impurity density, and a third amorphous silicon layer doped with impurity ions at a third impurity density lower than the first impurity density, and wherein the first to third amorphous silicon layers are stacked successively;
• forming hemispherical silicon grains on exposed surfaces of the remaining first conductive layer and the pillar;
• forming a dielectric layer on exposed surfaces of the pillar and the hemispherical silicon grains;
• and
• forming on the dielectric layer an upper electrode using a second conductive layer.

A method of forming a capacitor for a semiconductor device comprising:

• forming a lower electrode having a silicon layer with portions initially doped at different doping densities;
• forming a plurality of protrusions selectively on the lower electrode according to the different doping densities;
• forming a dielectric layer over the lower electrode and the protrusions;
• and
• forming an upper electrode over the dielectric layer.

A capacitor for a semiconductor device formed by a process comprising:

• forming a lower electrode having a silicon layer with portions initially doped at different doping densities;
• forming a plurality of protrusions selectively on the lower electrode according to the different doping densities;
• forming a dielectric layer over the lower electrode and the protrusions;
• and
• forming an upper electrode over the dielectric layer.