Semiconductor device and method for manufacturing the same

A method of forming a dual contact plug, comprising steps of:

• forming a source/drain region and a replacement gate structure on a semiconductor substrate, the replacement gate structure including a replacement gate;
• depositing a first inter-layer dielectric layer;
• planarizing the first inter-layer dielectric layer to expose the replacement gate in the replacement gate structure;
• completely removing the entire replacement gate to form an opening and depositing metal gate material into the opening to form a metal gate by means of replacement gate process;
• etching to form a first source/drain contact opening in the first inter-layer dielectric layer by means of lithography so that the source/drain region formed on the semiconductor substrate is exposed at the bottom of the first source/drain contact opening;
• sequentially depositing a liner and filling conductive metal in the first source/drain contact opening to form a first source/drain contact plug;
• depositing a second inter-layer dielectric layer on the first inter-layer dielectric layer with the first source/drain contact plug formed therein;
• etching to form a second source/drain contact opening and a gate contact opening in the second inter-layer dielectric layer by means of lithography so that the first source/drain contact plug is exposed at the bottom of the second source/drain contact opening and the metal gate is exposed at the bottom of the gate contact opening;
• and
• sequentially depositing a liner and filling conductive metal in the second source/drain contact opening and the gate contact opening to form a second source/drain contact plug and a gate contact plug.