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An individual identifier is easily provided in a semiconductor device capable of wireless communication. The semiconductor device includes a thin film transistor including a channel forming region, an island-like semiconductor film including a source region and a drain region, a gate insulating film

An individual identifier is easily provided in a semiconductor device capable of wireless communication. The semiconductor device includes a thin film transistor including a channel forming region, an island-like semiconductor film including a source region and a drain region, a gate insulating film, and a gate electrode; an interlayer insulating film; a plurality of contact holes formed in the interlayer insulating film which reach one of the source region and the drain region; and a single contact hole which reaches the other of the source region and the drain region, wherein a diameter of the single contact hole is larger than a diameter of each of the plurality of contact holes, and a sum of areas of bases of the plurality of contact holes is equal to an area of a base of the single contact hole.

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What is claimed is: 1. A semiconductor device comprising: a thin film transistor over a substrate including an island-like semiconductor film having a channel forming region, a source region, and a drain region, wherein a gate insulating film is formed adjacent to the island-like semiconductor film

What is claimed is: 1. A semiconductor device comprising: a thin film transistor over a substrate including an island-like semiconductor film having a channel forming region, a source region, and a drain region, wherein a gate insulating film is formed adjacent to the island-like semiconductor film, and a gate electrode is formed adjacent to the island-like semiconductor film; an interlayer insulating film over the thin film transistor; a plurality of first contact holes formed in the interlayer insulating film, wherein a base of each of the plurality of first contact holes has a first diameter and is in direct contact with one of the source region and the drain region; and a second contact hole formed in the interlayer insulating film, wherein a base of the second contact hole has a second diameter and is in direct contact with the other one of the source region and the drain region, wherein the second diameter is larger than the first diameter. 2. The semiconductor device according to claim 1, wherein the thin film transistor is used in a nonvolatile memory circuit. 3. The semiconductor device according to claim 1, further comprising: a side wall adjacent to a side surface of the gate electrode. 4. A semiconductor device comprising: a first thin film transistor over a substrate including a first island-like semiconductor film including a first channel forming region, a first source region, and a first drain region, wherein a gate insulating film is formed adjacent to the first island-like semiconductor film, and a first gate electrode is formed adjacent to the first island-like semiconductor film; a second thin film transistor over the substrate including a second island-like semiconductor film including a second channel forming region, a second source region, and a second drain region, wherein the gate insulating film is formed adjacent to the second island-like semiconductor film, and a second gate electrode is formed adjacent to the second island-like semiconductor film; an interlayer insulating film over the first thin film transistor and the second thin film transistor; a plurality of first contact holes formed in the interlayer insulating film, wherein a base of each of the plurality of first contact holes has a first diameter and is in direct contact with one of the first source region and the first drain region; a plurality of second contact holes formed in the interlayer insulating film, wherein a base of each of the plurality of second contact holes has a second diameter and is in direct contact with one of the second source region and the second drain region; and a third contact hole formed in the interlayer insulating film, wherein a base of the third contact hole has a third diameter and is in direct contact with either the other of the first source region and the first drain region or the other of the second source region and the second drain region, wherein the third diameter is larger than the first and second diameters. 5. The semiconductor device according to claim 4, wherein the first thin film transistor and the second thin film transistor are used in a nonvolatile memory circuit. 6. The semiconductor device according to claim 4, further comprising: a first side wall adjacent to a side surface of the first gate electrode; and a second side wall adjacent to a side surface of the second gate electrode. 7. A semiconductor device comprising: a first thin film transistor over a substrate including a first island-like semiconductor film including a first channel forming region, a first source region, and a first drain region, wherein a first gate insulating film is formed adjacent to the first island-like semiconductor film, and a first gate electrode is formed adjacent to the first island-like semiconductor film; a second thin film transistor over the substrate including a second island-like semiconductor film including a second channel forming region, a second source region, and a second drain region, a second gate insulating film is formed adjacent to the second island-like semiconductor film, and a second gate electrode is formed adjacent to the second island-like semiconductor film; an interlayer insulating film over the first thin film transistor and the second thin film transistor; a first contact hole formed in the interlayer insulating film and in contact with one of the first source region and the first drain region; a second contact hole formed in the interlayer insulating film and in contact with the other of the first source region and the first drain region; a plurality of third contact holes formed in the interlayer insulating film, wherein a base of each of the plurality of third contact holes has a third diameter and is in direct contact with one of the second source region and the second drain region; and a fourth contact hole formed in the interlayer insulating film, wherein a base of the fourth contact hole has a fourth diameter and is in direct contact with the other of the second source region and the second drain region, wherein the fourth diameter is larger than the third diameter. 8. The semiconductor device according to claim 7, wherein the second thin film transistor is used in a nonvolatile memory circuit, and the first thin film transistor is used in a logic circuit for controlling the nonvolatile memory circuit. 9. The semiconductor device according to claim 7, further comprising: a first side wall adjacent to a side surface of the first gate electrode; and a second side wall adjacent to a side surface of the second gate electrode.