MOSFET for an open-drain circuit and semiconductor integrated circuit device employing it

Abstract

In a conventional N-channel MOSFET for an open-drain circuit, when a positive static electric charge is applied to its drain, there is no route by way of which to discharge the static electric charge, resulting in a rather low static withstand voltage. To overcome this, according to the invention, an open-drain N-channel MOSFET has a drain region formed of an N-type semiconductor layer, a P-type impurity diffusion layer formed within the drain region, two high-concentration N-type impurity diffusion layers formed within the drain region so as to sandwich the P-type impurity diffusion layer, and a drain electrode connected to the P-type impurity diffusion layer and to the two high-concentration N-type impurity diffusion layers. When a positive static electric charge is applied to the drain, a parasitic transistor appears that forms a route by way of which the static electric charge is discharged.

1 - 4 . (canceled)  
   
   
       5 . A semiconductor integrated circuit device, comprising: 
 an output circuit,    wherein the output circuit comprises:    an open-drain N-channel MOSFET; and    an output terminal connected to a drain of the open-drain N-channel MOSFET,    wherein the open-drain N-channel MOSFET comprises:    a drain region formed of an N-type semiconductor layer;    a P-type impurity diffusion layer formed within the drain region;    two high-concentration N-type impurity diffusion layers formed within the drain region so as to sandwich the P-type impurity diffusion layer;    a low-concentration N-type impurity diffusion region formed in contact with the drain region; and    a drain electrode connected to the P-type impurity diffusion layer and to the two high-concentration N-type impurity diffusion layers,    wherein there are provided a plurality of the output circuit,    wherein the drain region and a source region of the open-drain N-channel MOSFET are formed in a pattern like teeth of a comb    wherein the source region and a backgate region are arranged on both sides of the drain region    wherein the output circuit includes a circuit that outputs a signal to the gate of the open drain N-channel MOSFET.    
   
   
       6 . A semiconductor integrated circuit device, comprising: 
 an output circuit,    wherein the output circuit comprises:    an open-drain N-channel MOSFET; and    an output terminal connected to a drain of the open-drain N-channel MOSFET,    wherein the open-drain N-channel MOSFET comprises:    a drain region formed of an N-type semiconductor layer;    a P-type impurity diffusion layer formed within the drain region;    two high-concentration N-type impurity diffusion layers formed within the drain region so as to sandwich the P-type impurity diffusion layer;    a low-concentration N-type impurity diffusion region formed in contact with the drain region; and    a drain electrode connected to the P-type impurity diffusion layer and to the two high-concentration N-type impurity diffusion layers,    wherein there are provided a plurality of the output circuit,    wherein a peripheral portion of the drain region of the open-drain N-channel MOSFET and a peripheral portion of a source region of the open-drain N-channel MOSFET have, as seen in a plan view, different shapes    wherein the output circuit includes a circuit that outputs a signal to the gate of the open drain N-channel MOSFET.    
   
   
       7 . (canceled)