Semiconductor device and manufacturing method thereof

Abstract

The high voltage transistor includes a first impurity layer, a second impurity layer formed inside the first impurity layer, so as to put the second impurity layer between them, a pair of third impurity layers and fourth impurity layers formed inside the first impurity layer, a fifth impurity layer formed from the uppermost surface of the first impurity layer to the inside of the first impurity layer so as to protrude along the main surface in the direction where the second impurity layer is disposed, and a conductive layer formed above the uppermost surface of the second impurity layer. The concentration of the impurity in the fourth impurity layer is higher than the concentration of the impurity in the third and the fifth impurity layers, and the concentration of the impurity in the fifth impurity layer is higher than the concentration of the impurity in the third impurity layer.

What is claimed is: 
     
         1 . A semiconductor device having transistors, in which the transistors each comprise:
 a semiconductor substrate having a main surface;   a first impurity layer formed over the main surface of the semiconductor substrate;   a second impurity layer formed inside the first impurity layer,   a pair of third impurity layers formed inside the first impurity layer so as to put the second impurity layer therebetween;   a fourth impurity layer formed in the inside of each of the pair of the third impurity layers;   a fifth impurity layer formed from an uppermost surface of the first impurity layer to the inside of the first impurity layer so as to protrude along the main surface from at least one of the third impurity layers in the direction where the second impurity layer is disposed; and   a conductive layer formed over the uppermost surface so as to at least partially overlap the second impurity layer and fifth impurity layer in a plan view,   wherein the second impurity layer is in direct physical contact with the fifth impurity layer and the second impurity layer extends towards the main surface of the substrate lower than the third impurity layers,   wherein entireties of the third impurity layers are spaced apart from the second impurity layer so that a portion of the first impurity layer and a portion of the fifth impurity layer are between the second impurity layer and the third impurity layer,   wherein a portion of the third impurity layer is directly between the fifth impurity layer and the fourth impurity layer,   wherein the concentration of the impurity in the fourth impurity layer is higher than the concentration of the impurity in the third and the fifth impurity layers,   wherein the impurity in the third and fifth impurity layers is a first conduction type impurity,   wherein the concentration of the first conduction type impurity in the fifth impurity layer is higher than the concentration of the first conduction type impurity in the third impurity layer,   wherein at least one of the third impurity layers and the second impurity layer are coupled by the fifth layer, and   wherein the impurity in the fourth impurity layer is a first conduction type impurity and the impurity in the second impurity layer is a second conduction type impurity.   
     
     
         2 . The semiconductor device according to  claim 1 ,
 wherein the fifth impurity layer is formed so as to couple both of the pair of third impurity layers and the second impurity layer.   
     
     
         3 . The semiconductor device according to  claim 1 ,
 wherein the pair of third and fourth impurity layers are disposed such that the position and the shape are symmetrical with respect to the second impurity layer.   
     
     
         4 . The semiconductor device according to  claim 1 ,
 wherein the concentration of the impurity in the fifth impurity layer is higher than the concentration of the impurity in the second impurity layer.   
     
     
         5 . The semiconductor device according to  claim 1 ,
 wherein the impurity in the first impurity layer and the impurity in the second impurity layer are impurity of an identical conduction type.