SEMICONDUCTOR INTEGRATED CIRCUIT DEVICE
A semiconductor integrated circuit device includes at least one MOS transistor that is formed in a main region of the circuit device. The main region has one conductivity type. The semiconductor integrated circuit device also includes a guard ring region formed surrounding the MOS transistor and in contact with the main region. The guard ring has the same conductivity type as the main region. The semiconductor integrated circuit device further includes an anode region formed facing the guard ring region and in contact with the main region. The anode region has the opposite conductivity type to the main region. The semiconductor integrated circuit device also includes a cathode region having at least a portion of the guard ring region. The anode region, the main region, and the cathode region form a diode.
1 . A semiconductor integrated circuit device comprising:
at least one MOS transistor that is formed in a main region having one conductivity type;
a guard ring region formed surrounding the MOS transistor and in contact with the main region, and having the one conductivity type;
an anode region formed facing the guard ring region and in contact with the main region, and having another conductivity type; and
a cathode region having at least a portion of the guard ring region, wherein the anode region, the main region, and the cathode region form a diode.
2 . The semiconductor integrated circuit device according to claim 1 , wherein the anode region is formed between the MOS transistor and the guard ring region.
3 . The semiconductor integrated circuit device according to claim 1 , wherein the anode region is electrically connected to a drain region of the MOS transistor.
4 . The semiconductor integrated circuit device according to claim 1 , wherein the anode region is formed in contact with a drain region of the MOS transistor.
5 . The semiconductor integrated circuit device according to claim 1 , wherein the main region is an n-well of a semiconductor substrate.
6 . The semiconductor integrated circuit device according to claim 1 , wherein the anode region has an elongated strip shape.
7 . The semiconductor integrated circuit device according to claim 1 , wherein the anode region has a rectangular shape.
8 . The semiconductor integrated circuit device according to claim 1 , wherein the anode region has an L shape.
9 . The semiconductor integrated circuit device according to claim 1 , wherein the diode is an electrostatic discharge protection diode.
10 . The semiconductor integrated circuit device according to claim 1 further comprising a second guard ring region around the diode.
11 . The semiconductor integrated circuit device according to claim 1 , wherein the main region is a part of a P-type semiconductor substrate.