Semiconductor device and method for manufacturing same

Abstract

A terrace insulating film (SL) to be overridden by a gate electrode (G) of an nLDMOS device is configured by LOCOS, and a device isolation portion (SS) is configured by STI. Furthermore, on an outermost periphery of an active region where a plurality of nLDMOS devices are formed, a guard ring having the same potential as that of a drain region (D) is provided. And, via this guard ring, the device isolation portion (SS) is formed in a periphery of the active region, thereby not connecting but isolating the terrace insulating film (SL) and the device isolation portion (SS) from each other.

1 . A semiconductor device comprising:
 a semiconductor substrate;   a semiconductor layer formed on the semiconductor substrate and having a main surface, the semiconductor layer having a trench formed on the main surface;   a device isolation portion formed in the trench and surrounding an active region of the semiconductor layer in plan view;   a source region formed in the active region;   a drain region formed in the active region;   a LOCOS film formed between the source region and the drain region in the active region;   a gate insulating film formed on the main surface between the source region and the drain region in the active region; and   a gate electrode formed on the gate insulating film and a portion of the LOCOS film;   wherein the LOCOS film has a thickness smaller than a thickness of the device isolation portion,   wherein the semiconductor substrate has a first conductivity type, and   wherein the semiconductor layer includes a first buried layer formed on the semiconductor substrate and has a second conductivity type different from the first conductivity type.   
     
     
         2 . The semiconductor device according to  claim 1 ,
 wherein the semiconductor layer includes a second buried layer having the first conductivity type in the same layer as the first buried layer and under the device isolation portion.   
     
     
         3 . The semiconductor device according to  claim 2 ,
 wherein the semiconductor layer includes a junction isolating part having the first conductivity type and formed between the second buried layer and the device isolation portion.   
     
     
         4 . The semiconductor device according to  claim 3 ,
 wherein the LOCOS film has a thickness smaller than or equal to 200 nm.   
     
     
         5 . The semiconductor device according to  claim 1 ,
 wherein the LOCOS film surrounds the source region in plan view.   
     
     
         6 . The semiconductor device according to  claim 5 ,
 wherein drain region surrounds the LOCOS film in plan view.   
     
     
         7 . The semiconductor device according to  claim 1 ,
 wherein the LOCOS film surrounds the source region and the drain region in plan view.   
     
     
         8 . The semiconductor device according to  claim 1 ,
 wherein the semiconductor substrate includes a first epitaxial layer formed thereon, and   wherein the first epitaxial layer has the first conductivity type.   
     
     
         9 . The semiconductor device according to  claim 1 ,
 wherein the semiconductor layer includes a second epitaxial layer formed on the first buried layer,   wherein the second epitaxial layer has the second conductivity type.   
     
     
         10 . The semiconductor device according to  claim 1 ,
 wherein the first conductivity type is p-type, and   wherein the second conductivity type is n-type.