Semiconductor device with a LOCOS trench

A method of manufacturing a gate controlled semiconductor device, the method comprising:

• forming a collector region of a first conductivity type;
• forming a drift region of a second conductivity type over the collector region;
• forming a body region of a first conductivity type over the drift region;
• forming at least one first contact region of a second conductivity type above the body region and having a higher doping concentration compared to the body region;
• forming at least one second contact region of a first conductivity type laterally adjacent to the at least one first contact region, the at least one second contact region having a higher doping concentration than the body region;
• forming at least one active trench extending from a surface into the drift region, wherein the at least one first contact region adjoins the at least one active trench so that a channel region is formed along said at least one active trench and within the body region, and
• wherein the at least one active trench comprises:
• two vertical sidewalls and a bottom surface between the two vertical sidewalls;
• and an insulation layer along the two vertical sidewalls and the bottom surface, wherein the insulation layer along at least one vertical sidewall comprises different thicknesses;
• forming at least one auxiliary trench extending from the surface into the drift region, and
• wherein the at least one auxiliary trench comprises:
• two vertical sidewalls and a bottom surface between the two vertical sidewalls;
• and an insulation layer along the two vertical sidewalls and the bottom surface, wherein the insulation layer along one vertical sidewall comprises different thicknesses and the insulation layer along another vertical sidewall comprises a constant thickness.

A method of manufacturing a gate controlled semiconductor device, the method comprising:

• forming a collector region of a first conductivity type;
• forming a drift region of a second conductivity type over the collector region;
• forming a body region of a first conductivity type over the drift region;
• forming at least one first contact region of a second conductivity type above the body region and having a higher doping concentration compared to the body region;
• forming at least one second contact region of a first conductivity type laterally adjacent to the at least one first contact region, the at least one second contact region having a higher doping concentration than the body region;
• forming at least one active trench extending from a surface into the drift region, wherein the at least one first contact region adjoins the at least one active trench so that a channel region is formed along said at least one active trench and within the body region, and
• wherein the at least one active trench comprises:
• two vertical sidewalls and a bottom surface between the two vertical sidewalls;
• and an insulation layer along the two vertical sidewalls and the bottom surface, wherein the insulation layer along at least one vertical sidewall comprises different thicknesses;
• forming at least one auxiliary trench extending from the surface into the drift region, and
• wherein the at least one auxiliary trench comprises:
• two vertical sidewalls and a bottom surface between the two vertical sidewalls;
• and an insulation layer along the two vertical sidewalls and the bottom surface, wherein the insulation layer along at least one vertical sidewall comprises a constant thickness;
• wherein at least two trenches of the at least one active trench and the at least one auxiliary trench are manufactured using the steps of:
• performing an etching process to form the two trenches laterally spaced from one another and forming a mesa region between the two trenches;
• then after performing the etching process, forming an insulation layer on the sidewalls of the two trenches;
• then after forming the insulation layer on the sidewalls of the two trenches:
• depositing a first filling material in the at least two trenches and on the mesa region;
• providing a mask;
• partially etching the first filling material such that an un-etched depth within the two trenches determines the dimension and regions for forming a thick insulation layer;
• depositing an oxidation barrier on top of the first filling material and the sidewalls of the two trenches;
• etching to remove the first filling material and oxidation barrier which are not on the sidewalls of the two trenches;
• and
• growing a thick insulation layer in regions which are not covered by the oxidation barrier.