Inductance device formed on semiconductor substrate

Abstract

According to a first aspect of the present invention, a plurality of PN junctions are formed at the surface of a semiconductor substrate under a belt-like conductive film having a spiral shape which constitutes an inductance device. An inverted bias voltage is applied to the PN junctions, and the surface of the substrate is completely depleted. Since the inverted bias voltage is applied to the PN junctions, even though the impurity density of the surface of the substrate is high and the adjacent PN junctions are separated to a degree, the extension of the depletion layers can be increased and complete depletion of the surface of the substrate can be achieved.

What is claimed is:  
     
         1 . An inductance device formed on a semiconductor substrate comprising: 
 a plurality of PN junctions formed at the surface of said semiconductor substrate; and    a belt-like conductive film having a coil shape and constituting said inductance device, formed on an insulating film over an area in which said plurality of PN junctions are formed,    wherein an inverted bias voltage is applied between said plurality of PN junctions, so that at the least a surface area of said semiconductor substrate is completely depleted.    
     
     
         2 . An inductance device according to    claim 1   , wherein said semiconductor substrate has one conductive type, 
 first impurity areas having an opposite conductive type, whose impurity density progressively increases from the surface of the substrate toward the inside of the substrate, are formed at said surface of said substrate, so that said PN junctions are formed, and    the inverted bias voltage applied to said first impurity areas is applied from a inside portion of said first impurity areas in said substrate.    
     
     
         3 . An inductance device according to    claim 2   , further comprising: 
 a second impurity area having said opposite conductive type, which is connected to said first impurity areas and is embedded in said substrate,    wherein said inverted bias voltage is applied through said second impurity area.    
     
     
         4 . A semiconductor device having an inductance device formed on a semiconductor substrate comprising: 
 an insulating area having a specific thickness, formed inward from the surface of said semiconductor substrate and formed by oxygen injection;    belt-like conductive film having a coil shape and constituting said inductance device, formed over the area in which the insulting area is formed;    a circuit element formed in a different area apart from said insulating area in said semiconductor substrate;    an insulating film, which is thinner than said insulating area, formed in an area where said circuit element is formed; and    a wiring layer connected to said circuit element and formed on said insulating film.    
     
     
         5 . An inductance device formed on a semiconductor substrate comprising: 
 an insulating film formed on the surface of said semiconductor substrate; and    a belt-like conductive film having a coil shape and constituting said inductance device, formed on said insulating film;    wherein a slit is formed in said belt-like conductive film in the direction of coil winding.    
     
     
         6 . An inductance device formed on a semiconductor substrate comprising: 
 an insulating film formed on the surface of said semiconductor substrate; and    a belt-like conductive film having a coil shape and constituting said inductance device, formed on said insulating film;    wherein for said belt-like conductive film a plurality of wiring patterns in the direction of coil winding are arranged parallely.    
     
     
         7 . An inductance device formed on a semiconductor substrate comprising: 
 an insulating film formed on the surface of said semiconductor substrate; and    a belt-like conductive film having a coil shape and constituting said inductance device, formed on said insulating film;    wherein said belt-like conductive film is made of a material having an anisotropic conductivity in which a conductivity in the direction of coil winding is larger than a conductivity in the direction perpendicular to said direction of coil winding.    
     
     
         8 . An inductance device according to    claim 7   , wherein said belt-like conductive film is made of an oxide superconductive material or an organic conductive material.