Semiconductor device and fabrication method thereof

A method of fabricating a semiconductor device, comprising:

• providing a substrate having a first conductivity type;
• forming a first trench and a second trench in the substrate, and filling up the first trench and the second trench with a conductive material;
• etching the conductive material in the first trench and the second trench to form a first recess on a first trench electrode and a second recess on a second trench electrode;
• depositing a first dielectric layer to fill up the first recess and the second recess to forma first dielectric portion on the first trench electrode and a second dielectric portion on the second trench electrode;
• etching the substrate to expose a plurality of sidewalls of the first dielectric portion and a plurality of sidewalls of the second dielectric portion;
• conformally forming a second dielectric layer on the substrate, the first dielectric portion and the second dielectric portion;
• etching back the second dielectric layer to form a plurality of first dielectric spacers on the sidewalls located on two opposite sides of the first dielectric portion and a plurality of second dielectric spacers on the sidewalls located on two opposite sides of the second dielectric portion, wherein the first dielectric portion and the first dielectric spacers constitute a first dielectric cap layer, and the second dielectric portion and the second dielectric spacers constitute a second dielectric cap layer;
• etching the substrate by using the first dielectric cap layer and the second dielectric cap layer as a mask to form a contact opening;
• and
• forming a conductive layer in the contact opening and on the first dielectric cap layer and the second dielectric cap layer, wherein the conductive layer includes an electrode contact located in the contact opening and between the first trench electrode and the second trench electrode.