Semiconductor device and method for forming gate structure thereof

A method for forming a semiconductor device, wherein a gate structure of the semiconductor device is formed by a method comprising:

• preparing a semiconductor substrate, and forming an active region on the semiconductor substrate, wherein the active region comprises an NMOSFET region and/or a PMOSFET region;
• forming a dummy gate stack, a gate sidewall spacer, N-type and/or P-type source/drain regions, and an interlayer dielectric layer on the active region sequentially;
• removing the dummy gate stack to form a gate opening, and forming an interface oxide layer and a ferroelectric gate dielectric layer sequentially at the gate opening;
• forming a stress sacrificial layer on the ferroelectric gate dielectric layer, and performing an annealing process;
• wherein during the annealing process, the clamping effect of the stress sacrificial layer induces the ferroelectric gate dielectric layer converted to form a ferroelectric-phase gate dielectric layer;
• removing the stress sacrificial layer;
• and
• forming a metal gate on the ferroelectric-phase gate dielectric layer.