Semiconductor device

Abstract

Aiming at realizing high breakdown voltage and low ON resistance of a semiconductor device having the super-junction structure, the semiconductor device of the present invention has a semiconductor substrate having an element forming region having a gate electrode formed therein, and a periphery region formed around the element forming region, and having an field oxide film formed therein; and a parallel p-n layer having n-type drift regions and p-type column regions alternately arranged therein, formed along the main surface of the semiconductor substrate, as being distributed over the element forming region and a part of the periphery region, wherein the periphery region has no column region formed beneath the end portion on the element forming region side of the field oxide film and has p-type column regions as at least one column region formed under the field oxide film.

Description

[0001] This application is based on Japanese patent applications No. 2005-258747 and No. 2006-122976 the contents of which are incorporated hereinto by reference. DISCLOSURE OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to a semiconductor device, and in particular to a semiconductor device having the super-junction structure. [0004] 2. Related Art [0005] Vertical power MOSFET has been proposed as a high-voltage-type MOS field effect transistor (MOSFET). Critical characteristics of this sort of high-voltage MOSFET include ON-resistance and breakdown voltage. The ON-resistance and the breakdown voltage depend on resistivity of an electric field moderating layer, wherein a trade-off relation resides in that lowering in the resistivity by raising the impurity concentration of the electric field moderating layer successfully results in reduction in the ON-resistance, but also in lowering in the breakdown voltage at the same time. [0006] In recent ...

AI Technical Summary

Benefits of technology

[0014] The present inventors found out that, when the p-type column regions were formed in the area straight under or generally under the end portion of the field oxide film used as the element isolation region, local points of concentration of the electric field occur on the periphery side of the column regions, and serve as determinant points of the breakdown voltage. This is ascribable to that the distance between the adjacent iso-potential surfaces under application of drain voltage becomes narrower on the field oxide film side, because dielectric constant of the field oxide film (3.9 for SiO2, for example) is smaller than that of Si (approximately 11.9). At around the end portion of the field oxide film, the iso-potential surfaces incline away from a plane parallel to the wafer surface, so that formation of the p-type column regions beneath the end portion of the field oxide film excessively narrows the distance between the iso-potential surfaces due to built-in potential created by the p-n junction at the peripherical side of such column region, and thereby produces the local points of concentration of electric field. The present inventors then found out that the tendency of excessive narrowing of the distance of the iso-potential surfaces on the peripherical side of the column regions can be suppressed, by avoiding formation of the p-type column regions beneath the end portion of the field oxide film, and finally completed the present invention.

[0018] By avoiding formation of the column regions straight under the end portion of the element isolation region provided in the periphery region as described in the above, the distance of the iso-potential surfaces formed over the parallel p-n region is prevented from being excessively narrowed in the vicinity of the element isolation region provided in the periphery region, and by providing the column regions also under the element isolation region, which means continuous provision of the column regions, the above-described, iso-potential surfaces become continuous also in the element isolation region similarly to as in the element forming region. The iso-potential surfaces now become less likely to cause discontinuity at the end portion of the element isolation region, and thereby concentration of the electric field is suppressed, so that the semiconductor device is realized as having a higher breakdown voltage in a stable manner, and also as having a low ON-resistance. It is therefore made possible to realize high breakdown voltage and low ON-resistance of the semiconductor device having the super-junction structure.

[0019] In conclusion, the present invention can realize high breakdown voltage and low ON-resistance of the semiconductor device having the super-junction structure.

Problems solved by technology

In this point of view, the configuration in the region corresponded to the boundary region described in the Japanese Laid-Open Patent Publication 2004-22716 is therefore considered as being insufficient, leaving room for improvement.

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