| 摘要 |
This concerns a semiconductor device such as a TTL-type integrated circuit device which has an input protection circuit for each inner circuit, e.g., each TTL logic gate. The input protection circuit is formed on a semiconductor substrate (2) having a first conductivity type, and comprises: a first impurity region (1) having a second conductivity type connected to an external terminal (3a) and having an island-shape formed on the semiconductor substrate and surrounded by an isolation region (2a) having the first conductivity type; a clamp diode (D1) comprising an electrode layer (4) contacting the first impurity region (1); and a PN junction type protection diode (D3) comprising a second impurity region (9) having the first conductivity type which crosses the first impurity region (1) between the clamp diode and a portion (3) of the first impurity region (1) connected to the external terminal, and which reaches the isolation region (23a). The reverse withstand voltage of the PN junction type protection diode (D3, 9-1) is smaller than that of the clamp diode (D1, 4-1) thereby avoiding permanent destruction of the clamp diode. |
