Semiconductor device and method for making the same
In a MOS-type semiconductor device in which, on a Si substrate, a SiGe layer having a valence band edge energy value smaller than a valence band edge energy value of the first semiconductor layer and a mobility larger than a mobility of the first semiconductor layer, a Si cap layer, and an insulating layer are sequentially laminated, the problem of the shift of the absolute value of the threshold voltage toward a smaller value caused by negative fixed charges formed in or near the interface between the Si cap layer and the insulting film by diffusion of Ge is overcome by neutralizing the negative fixed charges by positive charges induced in and near the interface between the Si cap layer and the insulating film along with addition of nitrogen atoms to the semiconductor device surface by NO gas annealing and thereby shifting the threshold voltage toward a larger value.
1. A method for making a semiconductor device, comprising:
forming on a first semiconductor layer a second semiconductor layer having a valence band edge energy value smaller than a valence band edge energy value of the first semiconductor layer and a mobility larger than a mobility of the first semiconductor layer,
forming on the second semiconductor layer a third semiconductor having a valence band edge energy larger than the valence band edge energy of the second semiconductor layer,
forming a semiconductor laminated structure by forming an insulating layer on the third semiconductor layer, the semiconductor laminated structure including negative fixed charges introduced into and near an interface between the third semiconductor layer and the insulating layer,
neutralizing the negative fixed charges by introducing positive fixed charges into and near the interface between the third semiconductor layer and the insulating layer, and
controlling a threshold voltage of a MOS transistor on the third semiconductor by introduction of positive fixed charges introduced into and near an interface between the first semiconductor layer and the second semiconductor layer, introduction of negative fixed charges into and near an interface between the second semiconductor layer and the third semiconductor layer and introduction of negative fixed charges into and near the interface between the third semiconductor layer and the insulating layer.
2. A method for making a semiconductor device, comprising:
forming on a first semiconductor layer a second semiconductor layer having a valence band edge energy value smaller than a valence band edge energy value of the first semiconductor layer and a mobility larger than a mobility of the first semiconductor layer,
forming on the second semiconductor layer a third semiconductor having a valence band edge energy larger than the valence band edge energy of the second semiconductor layer,
forming a semiconductor laminated structure by forming an insulating layer on the third semiconductor layer, and
controlling a threshold voltage of a MOS transistor on the third semiconductor by introduction of positive fixed charges introduced into and near an interface between the first semiconductor layer and the second semiconductor layer, introduction of negative fixed charges into and near an interface between the second semiconductor layer and the third semiconductor layer and introduction of negative fixed charges into and near the interface between the third semiconductor layer and the insulating layer.
3. A method for making a semiconductor device according to claim 2 , further comprising:
controlling the amount of positive fixed electrons introduced into and near an interface between the first semiconductor layer and the second semiconductor layer of the semiconductor laminated structure.
4. A method for making a semiconductor device according to claim 2 , further comprising:
introducing negative fixed electrons into and near an interface between the second semiconductor layer and the third semiconductor layer of the semiconductor laminated structure.
5. A method for making a semiconductor device according to claim 2 , further comprising:
introducing first positive fixed charges into and near an interface between the first semiconductor layer and the second semiconductor layer of the semiconductor laminated structure,
introducing negative fixed charges into and near an interface between the second semiconductor layer and the third semiconductor layer,
introducing second positive fixed charges into and near the interface between the third semiconductor layer and the insulating layer, and
controlling the total of the first positive fixed charges, the second positive fixed charges, and the negative fixed charges to a positive value.
6. The method for making the semiconductor device according to claim 5 , wherein the negative fixed charges are introduced along with diffusion of an element constituting the second semiconductor layer, and the positive fixed electrons are introduced along with addition of nitrogen atoms from outside.
7. The method for making the semiconductor device according to claim 6 , wherein the addition of nitrogen atoms is conducted through NO gas annealing.
8. The method for making the semiconductor device according to claim 6 , wherein the first semiconductor layer is Si, the second semiconductor layer is SiGe, the third semiconductor layer is Si, the element is Ge, and the insulating layer is silicon oxide.
9. The method for making the semiconductor device according to claim 8 , wherein the first semiconductor layer is n-type Si and the second semiconductor layer is n-type SiGe.
10. The method for making the semiconductor device according to claim 8 , wherein the first semiconductor layer is p-type Si and the second semiconductor layer is p-type SiGe.