Semiconductor device and method of manufacturing the same
A semiconductor device having a CMOS structure, wherein, in manufacturing a CMOS circuit, an impurity element which imparts p-type conductivity to the active layer of the p-channel type semiconductor device is added before forming the gate insulating film. Then, by applying thermal oxidation treatment to the active layer, the impurity element is subjected to redistribution, and the concentration of the impurity element in the principal surface of the active layer is minimized. The precise control of threshold voltage is enabled by the impurity element that is present in a trace quantity.
1. A method of manufacturing a semiconductor device, comprising the steps of:
forming a semiconductor island on an insulating surface;
introducing ions of a p-type impurity into at least a portion of the semiconductor island wherein the portion is to become a channel region of a transistor;
after introducing the ions of the p-type impurity, subjecting the semiconductor island to a thermal oxidization process to form a thermal oxide film on the semiconductor island, wherein the p-type impurity is incorporated into the thermal oxide film formed on the semiconductor island;
forming a gate electrode over the portion of the semiconductor island with the thermal oxide film interposed therebetween, wherein the gate electrode comprises crystalline silicon;
forming side walls on side surfaces of the gate electrode; and
forming a silicide layer on a top surface of the gate electrode by a salicide technique.
2. The method of manufacturing a semiconductor device according to claim 1 , wherein the ions are introduced without mass separation.
3. The method of manufacturing a semiconductor device according to claim 1 ,
wherein a concentration of the p-type impurity monotonically decreases from a first portion distant from an upper surface of the semiconductor island to a second portion close to the upper surface in a depthwise direction of the semiconductor island.
4. The method of manufacturing a semiconductor device according to claim 1 , where in the transistor is a p-channel transistor.
5. The method of manufacturing a semiconductor device according to claim 1 , wherein the silicide layer comprises cobalt silicide or titanium silicide.
6. A method of manufacturing a semiconductor device, comprising the steps of:
forming a semiconductor island on an insulating surface;
introducing a p-type impurity into only an edge portion of the semiconductor island; and
after introducing the p-type impurity, subjecting the semiconductor island to a thermal oxidization process to form a thermal oxide film on upper and side surfaces of the semiconductor island, wherein the p-type impurity is incorporated into the thermal oxide film;
forming a gate electrode over the semiconductor island with the thermal oxide film interposed therebetween, wherein the gate electrode contacts the thermal oxide film formed on the upper and side surfaces of the semiconductor island;
forming side walls on side surfaces of the gate electrode; and
forming a silicide layer on a top surface of the gate electrode by a salicide technique.
7. The method of manufacturing a semiconductor device according to claim 6 , wherein the semiconductor island is for an n-channel transistor.
8. The method of manufacturing a semiconductor device according to claim 6 , wherein the silicide layer comprises cobalt silicide or titanium silicide.
9. The method of manufacturing a semiconductor device according to claim 6 , wherein the semiconductor island is formed over a glass substrate.
10. The method of manufacturing a semiconductor device according to claim 6 , wherein the semiconductor island is formed over a silicon substrate.