PURPOSE: To prevent a conductive wiring layer and a semiconductor substrate from being short-circuited if a contact between polycrystalline silicon layer and a conductive wiring layer is formed by providing a second conductivity type impurity diffused layer on a lower region of a contact hole.

CONSTITUTION: An impurity diffused layer 18 is formed on a semiconductor substrate l under a contact hole 8. In the layer 18, an opposite conductivity type impurity to that to the substrate l is doped, and a p-n junction is formed in a boundary to the substrate 1. For example, when the substrate 1 is mounted and a positive bias voltage is applied to a conductive wiring layer 9, a reverse bias is applied to the p-n junction. Accordingly, even if the layer 9 is connected to the substrate 1 through a polycrystalline silicon layer 3 and an oxide film 2 at the bottom of the hole 8, an insulation between the layer 9 and the substrate l is obtained, no current leakage occurs through the substrate l. Thus, a desired bias voltage is effectively applied to the layer 3 as a field shielding electrode, and shielding characteristic is held excellently to provide satisfactory shielding characteristic.