1. Field of the Invention
The present invention relates to a semiconductor device and a method for manufacturing the semiconductor device.
In this specification, a “semiconductor device” refers to a device which can function by utilizing semiconductor characteristics; an electro-optical device, a semiconductor circuit, and an electronic device, each of which uses a semiconductor element, are all included in the semiconductor devices.
2. Description of the Related Art
In recent years, high-density integration of a device element has required miniaturization of each element. Here, one of the problems is a contact defect induced by miniaturization.
A contact defect refers to a malfunction generated when poor connection occurs at a portion where a wiring electrode and a semiconductor device are electrically connected to each other (hereinafter also referred to as contact). In particular, the necessity of electrical connection through a narrow contact hole provided in an interlayer insulating layer has been increased in accordance with a miniaturization technique and multilevel interconnection technique.
In the case of a narrow contact hole with a high aspect ratio required by the miniaturization of a semiconductor device, there are problems in that disconnection of a wiring electrode occurs in the contact hole due to a coverage defect of a conductive film for forming a wiring electrode and an upper portion of the contact hole is blocked by the conductive film due to overhang of the conductive film so that the wiring electrode cannot be formed in the contact hole.
In order to solve the above problems, as described in Patent Document 1 for example, a method for obtaining electrical connection by using columnar single crystal silicon has been proposed. This method includes the formation of a columnar single crystal of silicon, over a single crystal silicon substrate, by the vapor-liquid-solid (VLS) growth method using a low-melting-point metal material such as gold, followed by doping the columnar single crystal of silicon with an impurity to provide conductivity. The doped columnar single crystal of silicon is used as a connection electrode.
As another technique, as described in Patent Document 2, a method has been proposed in which after a contact hole is formed to expose a source region or a drain region of a transistor formed over a single crystal silicon substrate, an epitaxial silicon layer containing an impurity is formed in the contact hole to form a connection electrode.