FIELD-EFFECT TRANSISTOR AND SEMICONDUCTOR DEVICE

摘要

A field effect transistor and a semiconductor device are provided which enable a drain breakdown voltage in an off state and a drain breakdown voltage in an on state to be improved respectively. There are provided therein a field oxide film (31) disposed on an N-type drift region (20) positioned between a channel region of a silicon substrate (1) and an N-type drain (9), an N-type drift layer (21) disposed beneath the drift region (20) of the silicon substrate (1) and the drain (9), and an embedded layer (51) higher in P-type impurity concentration than the silicon substrate (1). The embedded layer (51) is disposed beneath the drift layer (21) except for below at least a portion of the drain (9) in the silicon substrate (1).