Semiconductor device and method for fabricating the same

Abstract

The semiconductor device of the present invention includes: a gate insulating film formed on a semiconductor region of a first conductivity type; a gate electrode formed on the gate insulating film; and a channel doped layer of the first conductivity type formed in the semiconductor region beneath the gate electrode. The channel doped layer contains carbon as an impurity.

Description

CROSS-REFERENCE TO RELATED APPLICATION [0001] This application is related to Japanese Patent Application No. 2004-279076 filed on Sep. 27, 2004, whose priority is claimed under 35 USC §119, the disclosure of which is incorporated herein by reference in its entirety. BACKGROUND OF THE INVENTION [0002] The present invention relates to semiconductor devices and methods for fabricating the devices, and more particularly relates to a MIS semiconductor device which can be reduced in size and has a doped layer having a shallow junction depth and a low resistance, and to a method for fabricating the semiconductor device. [0003] As the number of devices included in a semiconductor integrated circuit continues to increase, MIS transistors are required to be further reduced in size. To that end, MIS transistors need to have a channel doped layer having a shallow junction depth and a low resistance (see Japanese Laid-Open Publication No. 2002-33477, for example.) [0004] Hereinafter, with refere...

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Benefits of technology

[0015] To address the problems described above, it is therefore an object of the present invention to form a channel doped layer having steep dopant-concentration profiles having a shallow junction, thereby suppressing short channel effects, and also to enable the channel doped layer to be formed having a sufficient activation concentration and a low resistance, thereby realizing a miniaturized device capable of maintaining large driving force.

[0018] In the first inventive semiconductor device, the carbon added to the channel doped layer suppresses transient enhanced diffusion of a dopant in the channel doped layer, while increasing the activation rate of the introduced dopant. Thus, steep dopant-concentration profiles having a shallow junction, which are necessary to reduce the device size, are realized in the channel doped layer, while the sufficiently increased activation concentration permits the channel doped layer to have a low resistance, thereby allowing the semiconductor device to maintain a large driving force.

[0026] In the second inventive semiconductor device, the carbon added to the pocket doped layers formed below the sides of the gate electrode suppresses transient enhanced diffusion of a dopant in the pocket doped layers, while increasing the activation rate of the introduced dopant. Thus, steep dopant-concentration profiles having a shallow junction, which are necessary to reduce the device size, are realized in the pocket doped layers, while the sufficiently increased activation concentration in the pocket doped layers suppresses depletion in the channel doped layer, thereby making it possible to suppress short channel effects.

[0032] According to the first inventive semiconductor device fabrication method, the second dopant ions, made of carbon or made of molecules containing carbon, are selectively implanted into the channel formation region in the semiconductor region to form the carbon implantation layer in the channel implantation layer. Therefore, when the channel doped layer is formed through the later heat treatment, the carbon implanted as the impurity into the channel implantation layer suppresses transient enhanced diffusion of the first dopant in the channel doped layer, while increasing the activation rate of the implanted first dopant. As a result, steep dopant-concentration profiles having a shallow junction, which are necessary to reduce the device size, are realized in the channel doped layer, while the sufficiently increased activation concentration permits the channel doped layer to have a low resistance, thereby realizing a miniaturized device capable of maintaining a large driving force.

[0043] According to the second inventive semiconductor device fabrication method, the third dopant ions, made of carbon or made of molecules containing carbon, are selectively implanted into the pocket formation regions in the semiconductor region to form the pocket implantation layers. Therefore, when the pocket doped layers are formed through the subsequent heat treatment, the carbon implanted as the impurity into the pocket implantation layers suppresses transient enhanced diffusion of the second dopant in the channel doped layer, while increasing the activation rate of the implanted second dopant. Thus, steep dopant-concentration profiles having a shallow junction, which are necessary to reduce the device size, are realized in the pocket doped layers, while the sufficiently increased activation concentration in the pocket doped layers suppresses depletion more reliably. As a result, it is possible to suppress short channel effects and hence realize a miniaturized device capable of maintaining a large driving force.

Problems solved by technology

However, in the conventional semiconductor-device fabrication method, if indium ions are used as a dopant for forming doped layers such as the P-type channel doped layer 103 or the P-type pocket doped layers 107, a problem occurs in that the activation rate of the indium ions is low and hence sufficient activation concentration cannot be obtained.

As a result, transient enhanced diffusion (hereinafter simply referred to as “TED”) occurs, which also produces a problem in that abnormal diffusion of the indium is caused during the TED.

In many cases, those excess point defects are introduced due mainly to implantation damages resulting from ion implantation.

Therefore, even if indium ions having a relatively high mass number are implanted in order to obtain a shallower and steeper doped layer, the activation of the implanted indium ions serving as the dopant will be insufficient.

Therefore, with the conventional semiconductor-device fabrication method, it is difficult to form a shallow steep channel doped layer, which is required to reduce the transistor size, in such a manner that the channel doped layer has a sufficient activation concentration.

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