Semiconductor device having a ferroelectric memory and manufacturing method thereof
In a ferroelectric memory having a ferroelectric film between a gate electrode and a semiconductor substrate, dielectric breakdown of a gate insulating film is prevented and the polarization performance of the ferroelectric film is enhanced to improve the performance of a semiconductor device. In a memory cell including a field effect transistor including a control gate electrode formed over the semiconductor substrate, between the control gate electrode and a main surface of the semiconductor substrate, a paraelectric film and the ferroelectric film are formed by being stacked in this order over the main surface of the semiconductor substrate.
1. A semiconductor device, comprising:
a semiconductor substrate;
a first insulating film formed over the semiconductor substrate;
a ferroelectric film formed over the first insulating film; and
a first gate electrode formed over the ferroelectric film,
wherein the ferroelectric film comprises a first hafnium oxide film,
wherein the first insulating film has a dielectric constant higher than that of silicon nitride, and
wherein the first insulating film is a paraelectric film comprising a second hafnium oxide film.
2. The semiconductor device according to claim 1 , further comprising:
source and drain regions formed in an upper surface of the semiconductor substrate such that the first gate electrode is interposed therebetween.
3. The semiconductor device according to claim 1 , wherein the ferroelectric film has a thickness larger than that of the first insulating film.
4. The semiconductor device according to claim 1 , wherein an average grain diameter of a plurality of first crystals included in the ferroelectric film is larger than an average grain diameter of a plurality of second crystals included in the first insulating film.
5. The semiconductor device according to claim 1 , wherein an upper surface of the ferroelectric film has unevenness larger than that of an upper surface of the first insulating film.
6. The semiconductor device according to claim 1 , wherein the ferroelectric film and the first insulating film comprise the same material.
7. The semiconductor device according to claim 6 , wherein the ferroelectric film comprises a first crystal having an orthorhombic crystal phase, while the first insulating film comprises a second crystal having a non-orthorhombic crystal phase.
8. The semiconductor device according to claim 1 , wherein the first insulating film has an impurity concentration lower than that of the ferroelectric film.
9. The semiconductor device according to claim 1 , wherein, between the ferroelectric film and the first gate electrode, a metal film is additionally formed.
10. The semiconductor device according to claim 2 , further comprising:
a second gate electrode provided over the upper surface of the semiconductor substrate via a second insulating film to be adjacent to one side surface of the first gate electrode via the first insulating film and the ferroelectric film,
wherein the first gate electrode, the second gate electrode, and the source and drain regions are included in a nonvolatile storage element.
11. The semiconductor device according to claim 10 , further comprising:
a protruding portion which is a portion of the semiconductor substrate protruding from the upper surface of the semiconductor substrate and extending in a first direction along the upper surface of the semiconductor substrate,
wherein each of the first gate electrode and the second gate electrode extends in a second direction orthogonal to the first direction, and
wherein the source and drain regions are formed in a top surface of the protruding portion such that a pattern including the first gate electrode and the second gate electrode is interposed therebetween in the first direction.