Semiconductor device and method for protecting such device from a reversed drain voltage

摘要

An LDMOS field effect transistor (80) provides protection against the inadvertent reversal of polarity of voltage applied across the device. To protect an N-channel device, a floating P-type blocking region (82) is provided surrounding the drain region (32). The blocking region (82) is spaced apart from a body region (28) that forms the diffused channel (34) of the transistor (80). A first gate electrode (36) controls the conductivity of the diffused channel (34) and a second gate electrode (84) controls the conductivity of the surface (35) of the blocking region (82).