Abstract: In order to improve the characteristics of the high breakdown voltage MOS, a semiconductor device of the present invention is characterized in that an LDMOS transistor, which comprises a source region 4, a channel region 8, and a drain region 5, and a gate electrode 7 formed on the channel region 8, and a drift region formed between the channel region 8 and the drain region 5, wherein an N?-type low concentration layer 22 serving as the drift region is formed shallowly at least below the gate electrode 7 (first N?-type layer 22A) but formed deeply in a neighborhood of the drain region 5 (second N?-type layer 22B).

Abstract: A semiconductor device includes a source region 4, a channel region 8, a drain region 5 and a gate electrode which is patterned so that its side wall is tapered to be more narrow toward the top. A drift region 22 is formed between the channel region 8 and drain region 5 so as to be shallow below the gate electrode 7A (first N− layer 22A) and deep in the vicinity of the drain region 5 (second N− layer 22B). This configuration contributes to boosting the withstand voltage and reducing the “on” resistance of the semiconductor device.

Abstract: To enhance the withstand voltage of an LD MOS transistor, a method of fabricating a semiconductor device according to the invention is characterized in that a process for forming a drift region is composed of a step for implanting phosphorus ions and arsenic ions different in a diffusion coefficient into the superficial layer of a substrate, a step for forming a selective oxide film (a first gate insulating film) 9A and an element isolation film 9B by selective oxidation and diffusing the phosphorus ions and the arsenic ions and a step for implanting and diffusing boron ions, and in that in the step for forming the selective oxide film 9A and the element isolation film 9B by selective oxidation in a state in which an oxide film and a polycrystalline silicon film are laminated on the substrate, only a drift region formation region is selectively oxidized in a state in which the polycrystalline silicon film is removed.

Abstract: A semiconductor device includes a source region 4, a channel region 8, a drain region 5 and a gate electrode which is patterned so that its side wall is tapered to be more narrow toward the top. A drift region 22 is formed between the channel region 8 and drain region 5 so as to be shallow below the gate electrode 7A (first N−layer 22A) and deep in the vicinity of the drain region 5 (second N−layer 22B). This configuration contributes to boosting the withstand voltage and reducing the “on” resistance of the semiconductor device.

Abstract: A semiconductor device includes a source region 4, a channel region 8, a drain region 5 and a gate electrode which is patterned so that its side wall is tapered to be more narrow toward the top. A drift region 22 is formed between the channel region 8 and drain region 5 so as to be shallow below the gate electrode 7A (first N− layer 22A) and deep in the vicinity of the drain region 5 (second N− layer 22B). This configuration contributes to boosting the withstand voltage and reducing the “on” resistance of the semiconductor device.

Abstract: Disclosed is a method of manufacturing a semiconductor device which includes a source region, a channel region, a drain region, a gate electrode formed on the channel region through a gate insulating film 6 and a drift region (N− layer 22) formed between the channel region and the drain region, wherein the process of forming the drift region (N− layer) comprises the steps of: ion-implanting and diffusing at least two kinds of second conduction type impurities (e.g. phosphorus and arsenic ions) having different diffusion coefficients in a P-type well region 21; ion-implanting at least one kind first conduction type impurities (e.g. boron ions) having a diffusion coefficient substantially equal to or larger than that of at least one of said second conduction type impurities (e.g. phosphorus); and diffusing the first conduction type impurities after the gate insulating film 6 has been formed.