Patent ID: 7544620

Claim:
A method for digging a deep trench in a body of semiconductor material, comprising: on a surface of a semiconductor body, forming a mask having at least one opening; forming a passivating layer conformally on said mask and on said semiconductor body within said opening; and executing a directional etch so as to first remove said passivating layer at least from above said semiconductor body and then etch said semiconductor body through said opening; wherein said steps of forming a passivating layer and executing a directional etch are carried out repeatedly in sequence so as to form a first portion of a trench through said opening, said first portion of said trench including at least one corrugated spacing portion having a width increasing as a distance from said surface increase; and further comprising executing a polymerizing plasma etch in the first portion of said trench, said polymerizing plasma etch including simultaneously etching the semiconductor body while forming a protective layer of increasing thickness on side surfaces of the opening to form a tapered second portion of said trench, having a traverse dimension decreasing as a distance from said surface increases.