Semiconductor device having a protection circuit with lateral bipolar transistor
First Claim
1. A semiconductor device including a semiconductor substrate of a first conductivity type, at least one terminal for providing at least one of input and output signals, a protection circuit and an inner element, said protection circuit comprising:
- a first protective element comprising a diode having a first impurity region of a second conductivity type opposite to said first conductivity type of said substrate, a first end of said first impurity region being connected to said terminal; and
a second protective element comprising a lateral bipolar transistor having a collector region and an emitter region, both of said collector and emitter regions having the second conductivity type, being formed in said substrate, being arranged to but separate from each other so as to define a base region in said substrate, and being shallower than said first impurity region, a first end of said collector region being connected to a second end of said first impurity region that is spaced from said first end thereof, a second end of said collector region being connected to said inner element, and said emitter region being electrically connected to ground;
wherein said terminal, said first protective element, said second protective element and said inner element are operatively connected in series in the recited order, and said first protective element has a higher surge capacity and higher junction breakdown voltage than that of said second protective element as a result of said first impurity region and said collector region;
so that a protection voltage corresponding to said at least one of said input and output signals is provided by said protection circuit to said inner element.
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Abstract
A protection circuit for inner elements such as metal insulator semiconductor (MIS) field effect transistors in a semiconductor device of high packing density has been improved. The protection circuit comprises protective elements of two types. One type has a deep diffusion region providing the element with high surge capacity, that is an ability to withstand the energy of an incoming surge, and the other type has a shallow diffusion region providing a low breakdown voltage. With a combination of these two types of protective element, the protection circuit can withstand high energy of an input surge and, at the same time, provide a low protection voltage suitable to protect the inner elements from breakdown.
44 Citations
15 Claims
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1. A semiconductor device including a semiconductor substrate of a first conductivity type, at least one terminal for providing at least one of input and output signals, a protection circuit and an inner element, said protection circuit comprising:
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a first protective element comprising a diode having a first impurity region of a second conductivity type opposite to said first conductivity type of said substrate, a first end of said first impurity region being connected to said terminal; and a second protective element comprising a lateral bipolar transistor having a collector region and an emitter region, both of said collector and emitter regions having the second conductivity type, being formed in said substrate, being arranged to but separate from each other so as to define a base region in said substrate, and being shallower than said first impurity region, a first end of said collector region being connected to a second end of said first impurity region that is spaced from said first end thereof, a second end of said collector region being connected to said inner element, and said emitter region being electrically connected to ground; wherein said terminal, said first protective element, said second protective element and said inner element are operatively connected in series in the recited order, and said first protective element has a higher surge capacity and higher junction breakdown voltage than that of said second protective element as a result of said first impurity region and said collector region; so that a protection voltage corresponding to said at least one of said input and output signals is provided by said protection circuit to said inner element. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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Specification