Semiconductor device and method for fabricating the same

A semiconductor device comprising:

• a first impurity region disposed in a substrate;
• a second impurity region disposed in the substrate and spaced apart from the first impurity region;
• a bit line contact plug disposed over the first impurity region and having a multi-tapered sidewall;
• and
• a storage contact plug disposed over the second impurity region,
• wherein the multi-tapered sidewall of the bit line contact plug includes at least one inflection point at which a slope changes, and
• wherein the at least one inflection point is disposed higher than a bottom surface of the storage contact plug.

A method for fabricating a semiconductor device, the method comprising:

• forming a first impurity region and a second impurity region in a substrate;
• forming a bit line contact hole that exposes the first impurity region and has a multi-tapered sidewall;
• forming a bit line contact plug that fills the bit line contact hole and includes a lower buried portion contacting the first impurity region and an upper buried portion over the lower buried portion;
• forming a gap-fill layer in a peripheral area of the lower buried portion of the bit line contact plug;
• side-recessing a sidewall of the upper buried portion of the bit line contact plug;
• and
• forming a storage contact plug that contacts the second impurity region.