Method for manufacturing metal gate of PMOS

A method for manufacturing a metal gate of a PMOS, comprising steps of:

• step 1, forming a P-type work function metal layer, the P-type work function metal layer being formed on a bottom surface and a side surface of a gate trench;
• step 2, depositing an N-type work function metal layer by means of a physical vapor deposition (PVD) process, the N-type work function metal layer being formed on a surface of the P-type work function metal layer, wherein over the bottom surface of the gate trench, the N-type work function metal layer has a hill profile composed of a thicker portion located at a middle area of the gate trench and a thinner portion located at the side surface of the gate trench, and the hill profile enables the N-type work function metal layer to have a sharp corner less than 90 degrees at a corner of the gate trench;
• step 3, forming a first top barrier metal sublayer on a surface of the N-type work function metal layer by means of a conformal growth process, wherein, due to properties of conformal growth, the first top barrier metal sublayer completely fills a sharp corner area of the N-type work function metal layer at the corner of the gate trench;
• step 4, growing a second top barrier metal sublayer by means of a PVD bombardment process, wherein the PVD bombardment process increases a vertical bias while growing the second top barrier metal sublayer, so as to achieve vertical bombardment on the first top barrier metal sublayer and the second top barrier metal sublayer, increasing atomic density of the first top barrier metal sublayer and causing sputtering of materials of the first top barrier metal sublayer and the second top barrier metal sublayer that are deposited at the middle area on the bottom surface of the gate trench to the corner of the gate trench, thereby increasing a thickness of a stack layer of the first top barrier metal sublayer and the second top barrier metal sublayer at the corner of the gate trench and making an opening profile of the second top barrier metal sublayer in the gate trench be U-shaped;
• step 5, sequentially forming a third top barrier metal sublayer and a fourth top barrier metal sublayer by means of a PVD process, wherein the first top barrier metal sublayer, the second top barrier metal sublayer, the third top barrier metal sublayer, and the fourth top barrier metal sublayer are stacked to form a top barrier metal layer;
• and
• step 6, forming a metal conductive material layer to completely fill the gate trench.