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From the background information supplied by the inventors, news correspondents obtained the following quote: "The technology disclosed herein relates to semiconductor devices and methods for fabricating the semiconductor devices, and more particularly, to laterally diffused metal oxide semiconductor (LDMOS) transistors, which have a low on resistance while keeping a sufficient breakdown voltage, and methods for fabricating the LDMOS transistors.
"In recent years, as the performance, multi-functionality, and power consumption of electronic apparatuses have been improved, there has been a demand for semiconductor devices incorporated in the electronic apparatus which have a higher breakdown voltage, higher power, a smaller size, lower power consumption, etc. Among the semiconductor devices, even in the fields of driver IC, power supply IC, etc., there has been a demand for MOS electric field effect transistors (MOSFETs) which have a lower on resistance while keeping the breakdown voltage at a predetermined level in order to achieve lower power consumption.
"To meet the demand, an LDMOS transistor has been proposed in which the channel region is formed by ion implantation and thermal treatment, whereby a short-channel device can be formed independently of the accuracy of a mask. In the LDMOS transistor, the on resistance can be reduced by decreasing the channel resistance component. Note that there is typically a trade-off between the on resistance and the breakdown voltage, and this also holds true for the LDMOS transistor. Therefore, a LOCOS offset LDMOS transistor has been proposed in which, in order to keep a sufficient breakdown voltage, a thick oxide film is formed by LOCOS between the drain region and an end portion of the gate electrode so that the gate electrode end portion is offset from the drain region (the position of the effective gate end portion is shifted), whereby an electric field concentrated at the gate electrode end portion can be reduced.
"FIG. 17 is a cross-sectional view of a typical LDMOS transistor. Here, the LDMOS transistor (semiconductor device) is of N-channel type.
"As shown in FIG. 17, the typical semiconductor device includes an LOCOS oxide film 303, a p-type body diffusion region 302, an n-type source diffusion region 306, and an n-type drain diffusion region 307 which are formed in an upper portion of an n-type semiconductor substrate 301. The source diffusion region 306 is formed in an upper portion of the body diffusion region 302. The LOCOS oxide film 303 is formed between the source diffusion region 306 and the drain diffusion region 307, and is spaced apart from the body diffusion region 302.
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