Semiconductor device having high density interconnections and method for manufacturing the same

Abstract

A main electrode region of a semiconductor element is provided in a semiconductor region on the surface of a semiconductor substrate, and first and second interlayer insulating films are deposited on this semiconductor region. A metal interconnection is provided on top of the second interlayer insulating film. The main electrode region and the metal interconnection a shape having a first tapered portion with an isotropic taper angle &thgr;3, which starts from the interface between the first and second interlayer insulating films, and a second tapered portion with an anisotropic taper angle &thgr;4, which starts from a point within the second interlayer insulating film. As a result, the shape of the face of the contact plug connecting to the metal interconnection is anisotropic, having dimensions which are greater in the direction parallel to the metal interconnection than in the direction perpendicular to the metal interconnection. The shoulders of the contact hole which are parallel to the metal interconnection are smoothed by anisotropic recession caused by the second tapered portion. Therefore, barrier metal film can be deposited approximately evenly inside the contact hole. Since the diameter of the contact hole does not increase perpendicular to the metal interconnection due to the anisotropic taper angle &thgr;4, the intervals between adjoining metal interconnections can be minimized. The metal interconnection and the contact plug can be comprised from the same conductor or different conductors. The metal interconnection may, for instance, be a DRAM bit line or the like.