Method of manufacturing a semiconductor device

Abstract

To provide a semiconductor device and a manufacturing method thereof achieving both reduction in ON resistance and increase in breakdown voltage and suppressing a short circuit. The semiconductor device has, in its semiconductor substrate having a main surface, a p − type epitaxial region, n − type epitaxial region, n type offset region, and p type body region configuring a pn junction therewith; and further has a p + type buried region between the p − type and n − type epitaxial regions, isolation trench extending from the main surface to the p + type buried region, and trench sidewall n type region formed on at least a portion of the sidewall of the isolation trench. The n type impurity concentration in the trench sidewall n type region is higher than that in the n − type epitaxial region. The trench sidewall n type region extends along the sidewall to reach the p + type buried region.

What is claimed is: 
     
         1 . A method of manufacturing a semiconductor device, comprising:
 providing a semiconductor substrate having a main surface and a first conductivity type first region;   forming, in the semiconductor substrate and over the first region on the main surface side, a first conductivity type buried region having a first conductivity type impurity concentration higher than that of the first region;   forming, in the semiconductor substrate and over the first region and the buried region on the main surface side, a second conductivity type second region;   forming, in the semiconductor substrate and over the second region on the main surface side, a second conductivity type third region;   forming an isolation trench extending so as to surround the periphery of an element region including the third region and reach the buried region from the main surface;   forming a second conductivity type trench sidewall high concentration region over at least a portion of the sidewall of the isolation trench on the side of the element region; and   forming a first conductivity type fourth region in the semiconductor substrate so as to be adjacent to the third region and configure a pn junction therewith over the second region on the main surface side,   wherein the second conductivity type impurity concentration in the trench sidewall high concentration region is higher than the second conductivity type impurity concentration in the second region,   wherein the trench sidewall high concentration region extends along the sidewall to reach the buried region, and   wherein the first conductivity type is p type, and the second conductivity type is n type.   
     
     
         2 . The method of manufacturing a semiconductor device according to  claim 1 ,
 wherein in the forming a trench sidewall high concentration region, a second conductivity type impurity is ion-implanted from an oblique direction with respect to the sidewall.