Semiconductor device and method for manufacturing the same

Abstract

A semiconductor device which eliminates the need for high fillability through a simple process and a method for manufacturing the same. A high breakdown voltage lateral MOS transistor including a source region and a drain region is completed on a surface of a semiconductor substrate. A trench which surrounds the transistor when seen in a plan view is made in the surface of the semiconductor substrate. An insulating film is formed over the transistor and in the trench so as to cover the transistor and form an air-gap space in the trench. Contact holes which reach the source region and drain region of the transistor respectively are made in an interlayer insulating film.

What is claimed is: 
     
       1. A semiconductor device comprising:
 a semiconductor substrate having a trench in a main surface thereof, the semiconductor substrate having a first conductivity type which is one of an n-type and a p-type; 
 a device being formed over the main surface of the semiconductor substrate; and 
 an insulating film being formed over the device and in the trench so as to cover the device and form an air-gap space in the trench, wherein 
 a side surface of the trench on a same level of a bottom of the air-gap space directly contacts reaches into the semiconductor substrate, 
 the semiconductor substrate includes a buried layer having a second conductivity type which is the other one of the n-type and the p-type, and 
 the trench penetrates the buried layer. 
 
     
     
       2. A semiconductor device according to  claim 1  wherein,
 the device has a conductive portion, and 
 the insulating film has a hole which reaches the conductive portion. 
 
     
     
       3. A semiconductor device according to  claim 1 , wherein the trench is formed so as to surround the device entirely when seen in a plan view. 
     
     
       4. A semiconductor device comprising:
 a semiconductor substrate having a trench in a main surface thereof, the semiconductor substrate having a first conductivity type which is one of an n-type and a p-type;   a conductive portion formed over the main surface of the semiconductor substrate; and   an insulating film formed over the conductive portion and in the trench to cover the conductive portion and form an air-gap in the trench, wherein   a bottom of the air-gap reaches into the semiconductor substrate,   the semiconductor substrate includes a buried layer having a second conductivity type which is the other one of the n-type and the p-type, and   the trench penetrates the buried layer.   
     
     
       5. The semiconductor device according to claim 4 wherein, the insulating film has a hole which reaches the conductive portion. 
     
     
       6. The semiconductor device according to claim 4, wherein the trench surrounds the conductive portion entirely when seen in a plan view. 
     
     
       7. A semiconductor device comprising:
 a first semiconductor layer having a first conductivity type which is one of an n-type and a p-type;   a second semiconductor layer, on the first semiconductor layer, having a second conductivity type which is the other one of the n-type and the p-type;   a third semiconductor layer, on the second semiconductor, having the first conductivity type which is the one of the n-type and the p-type;   a MOS transistor having a gate electrode over the third semiconductor layer, and source and drain regions in the third semiconductor layer;   a first isolation region having a first trench penetrating the third semiconductor layer and the second semiconductor layer to reach inside the first semiconductor layer, the first trench surrounding the MOS transistor;   a first insulating film covering the gate electrode and filling in the first trench, while leaving an air-gap in the first trench, and   a bottom of the air-gap reaches into one of the first to third semiconductor layers.   
     
     
       8. The semiconductor device according to claim 7, further comprising a second isolation region having a second trench disposed in the third semiconductor layer, the second trench being filled with a second insulating film, the second isolation region contacting the source or drain region in the third semiconductor layer, wherein
 the second trench is shallower than the first trench.   
     
     
       9. The semiconductor device according to claim 8, wherein the first trench surrounds the second isolation region and the MOS transistor. 
     
     
       10. The semiconductor device according to claim 9, wherein the bottom of the air-gap is located in the first semiconductor layer. 
     
     
       11. The semiconductor device according to claim 10, wherein the air-gap extends from the third semiconductor layer to the first semiconductor layer. 
     
     
       12. The semiconductor device according to claim 11, wherein the first semiconductor layer includes a semiconductor substrate and an epitaxial region formed on the semiconductor substrate. 
     
     
       13. The semiconductor device according to claim 9, further comprising:
 an interconnecting layer on the first insulating film; and   a conductive layer, in the first insulating film, connecting the interconnecting layer and one of the source region and the drain region of the MOS transistor.   
     
     
       14. The semiconductor device according to claim 8, further comprising a third insulating film between the first insulating film and the gate electrode. 
     
     
       15. The semiconductor device according to claim 14, wherein
 the first insulating film is a silicon oxide film, and   the third insulating film is a silicon nitride film.   
     
     
       16. The semiconductor device according to claim 9, further comprising another second isolation region having another second trench disposed in the third semiconductor layer, the another second trench being filled with the second insulating film, the another second trench is shallower than the first trench, wherein
 the first trench penetrates the second insulating film in the another second trench.