Lateral double-diffused metal oxide semiconductor field effect transistor (ldmosfet) with a below source isolation region and a method of forming the ldmosfet

Abstract

Disclosed are a field effect transistor (FET) (e.g., a lateral double-diffused metal oxide semiconductor field effect transistor (LDMOSFET)) and a method of forming the FET. In the FET, an etch stop pad is on a semiconductor substrate (e.g., a P-type silicon substrate). A semiconductor layer (e.g., a silicon layer) is also on the substrate and extends laterally over the etch stop pad. A first well region (e.g., an N-well region) extends through the semiconductor layer into the substrate such that it contains the etch stop pad. A second well region (e.g., a P-well region) is in the first well region aligned above the etch stop pad. A source region (e.g., a N-type source region) is in the second well region. A buried isolation region (e.g., a buried air-gap isolation region) is within the first well region aligned below the etch stop pad so as to limit vertical capacitor formation.