US Patent 7087957 Semiconductor device and manufacturing method of the same

A semiconductor device includes a compound semiconductor substrate, a channel layer provided on the compound semiconductor substrate, a buried layer provided on the channel layer, a first recess formed in the buried layer in an E-mode region, a second recess formed in the first recess in the E-mode region and another second recess formed in the buried layer in a D-mode region, and a gate electrode provided in the second recess in the E-mode region and another gate electrode provided in the second recess in the D-mode region, and a distance between a surface of the buried layer and a bottom of the second recess in the E-mode region is shorter than another distance between another surface of the buried layer and a bottom of said another second recess in the D-mode region.