Semiconductor device and manufacturing method thereof

A semiconductor device, comprising:

• two gate stack layers, disposed on a semiconductor substrate, wherein each of the gate stack layers comprises a first side and a second side opposite to the first side, and each gate stack layer comprises a first gate layer and a second gate layer, the first gate layer is an L-shaped structure;
• two conductive structures with a same width, respectively disposed at the first side, wherein each of the conductive structures comprises a vertical surface and a bottom surface;
• two L-shaped dielectric layers disposed at the first side respectively, wherein each L-shaped dielectric layer contacts one of the gate stack layers and one of the bottom surfaces of the conductive structures directly;
• another conductive structure disposed between the two gate stack layers;
• a trench disposed within the another conductive structure, wherein the trench has a planar bottom surface;
• and
• a cap layer discretely disposed over the semiconductor substrate, wherein portions of the cap layer fill up the trench and other portions of the cap layer are disposed on the conductive structures, and top surfaces of the conductive structures respectively disposed at the first sides are exposed from the cap layer.