A lead frame substrate, includes: a metal plate having first and second surfaces; a semiconductor element mounting section, semiconductor element electrode connection terminals, and a first outer frame section formed on the first surface; external connection terminals formed on the second surface and electrically connected with the semiconductor element electrode connection terminals; a second outer frame section formed on the second surface; and a resin layer formed on a gap between the first outer frame and the second outer frame. Each external connection terminal buried in the resin layer has at least one projection formed on a side surface thereof throughout a side lower portion of the first surface.