With recent process miniaturization, the number of processing steps necessary to manufacture a nonvolatile memory such as a flash memory has been increasing. Increases in the numbers of times of deposition, etching, and exposure cause more defects on a semiconductor substrate, and therefore it becomes difficult to ensure reliability of a capacitance element including a gate oxide film on semiconductor substrate.
For example, JP-A-Heisei 2-76251 (Patent Literature 1) discloses a technique that automatically prevents defective operation due to insulation breakdown in a device including a large scale capacitance unit such as a charge pump circuit. A polysilicon electrode PSi divided into a plurality of sections is present on the surface of a semiconductor substrate, and an oxide film is present between the polysilicon electrode sections PSi and the semiconductor substrate, to form a capacitance. The polysilicon electrode sections are connected with narrow aluminum wiring lines Al.
In an ordinary state, the polysilicon electrode sections are all connected with a same wiring line, and therefore the plurality of electrode sections can operate as an integrated capacitance element. If an oxide film for a capacitance is broken through a specific polysilicon electrode portion in a state that a voltage difference is supplied between the substrate and the electrode, leakage current flows, concentrating on a broken electrode portion. In this case, a wiring line for connection between the electrode sections is narrow, and therefore the wiring line connected to the broken electrode section is fused and disconnected by an extraordinary leakage current due to the insulation breakdown to separate the broken polysilicon electrode section from the device.
In this technique, a fuse function for removing the defective device is covered by the wiring line. However, in the recent miniaturized process, to stably fabricate a narrow wiring line as a process node serving as the fuse is difficult in terms of a fabrication method. At a miniaturized process node, influence of a variation on a wiring line width is large, and therefore it is difficult to equalize a current value at which the fuse disconnects the connection to an arbitrary value.
Also, JP2003-338553A (Patent Literature 2) discloses a technique related to a semiconductor device provided with a nonvolatile memory that interrupts a leakage current to a broken electrostatic protective component.