Semiconductor device and manufacturing method thereof

Abstract

The present invention provides a semiconductor device that reduces the junction leak current and achieves an improvement in the reliability of the gate oxide film by minimizing divot formation and the occurrence of a kink and a method of manufacturing such a semiconductor device. A pad oxide film and a silicon nitride film are formed on an Si substrate and a groove-like trench is formed through photolithography and etching. The liner oxide of the trench are oxidized through oxidizing / nitriding. Then, the trench is filled with an insulating film, the insulating film is planarized and the silicon nitride film and the pad oxide film are removed. Next, a field area is formed and a transistor is formed by following specific steps. By forming a trench liner oxide film containing nitrogen, stress is reduced.

Description

BACKGROUND OF THE INVENTION[0001]The present invention relates to a structure of an element isolation region in a semiconductor device and a semiconductor device manufacturing method.[0002]In a semiconductor device having silicon as its main constituent, an element isolation region (hereafter referred to as a field area) is formed through the LOCOS (local oxidation of silicon) method or the STI (shallow trench isolation) method to electrically isolate elements in the prior art. An area other than the field area is referred to as an active area, and the elements are formed in the active area. When a field area is formed through the LOCUS method, a bird's beak is formed at an end of the field area, reducing the size of the area that can be utilized as active area. With further miniaturization of elements achieved in recent years, the width and the pitch of the active area have become smaller and the use of the LOCOS method to form the field area is problematic. In contrast, the STI me...

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Benefits of technology

[0008]An object of the present invention, which has been completed by addressing the problems discussed above, is to provide a semiconductor device through which the junction leak current can be reduced and the reliability of the gate oxide film can be improved by minimizing divot formation and the occurrence of a kink, and a method of manufacturing the semiconductor device.

[0009]In order to achieve the object described above, in a first aspect of the present invention, a semiconductor device provided with a groove-like trench at the isolation region, with an oxide film containing nitrogen used to constitute a liner oxide film in the trench, is provided. By using an oxide film containing nitrogen to constitute the liner oxide film, the degree of distortion occurring in the structure within the oxide film can be lessened. In addition, the compressive stress in the trench liner oxide film, the stress at the edge of the active area and the tensile stress imparted to the Si substrate are all reduced. Thus, the formation of crystal defects, the junction leak current and the occurrence of a kink are minimized.

[0010]In a second aspect of the present invention, a semiconductor device provided with a groove-like trench located at an isolation region, with nitrogen contained in the composition of the surface of an isolation film within the trench, is provided. Since the HF resistance is improved by adopting this structure, divots are less likely to be formed during the subsequent HF process.

Problems solved by technology

With further miniaturization of elements achieved in recent years, the width and the pitch of the active area have become smaller and the use of the LOCOS method to form the field area is problematic.

When this area becomes exposed, numerous problems arise with regard to the occurrence of stress which is to be detailed later.

The presence of a kink results in electrical characteristics different from the design electrical characteristics, and thus, the transistor characteristics cannot be identified.

In addition, since parasitic transistors and kinks manifesting under these circumstances are not uniform, the transistor characteristics cannot be determined with uniformity during the production, which, in turn, results in inconsistency in transistor characteristics.

Furthermore, occurrence of stress induces a dislocation, resulting in the formation of crystal defects.

When the impurity concentration is reduced, a depletion layer is more readily extended compared to the other areas, to lead to an increase in the junction leak current of via the crystal defects.

When the film thickness is reduced, the reliability of the gate oxide film 92 becomes an issue.

An electric field concentration is considered to be one of the causes of kinks and is, therefore, not desirable.

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