A semiconductor device and method of its manufacture

A semiconductor device comprising a vertical stack of layers, comprising: an active layer configured to support a two dimensional carrier gas having an excess of carriers; source and drain contacts provided to said active layer such that a current can flow between said source and drain contacts through said two dimensional carrier gas; a lower conducting region,    wherein said lower contact conducting region is a patterned lower conducting region such that said active layer is suspended across gaps in said lower conducting region and said active layer is physically supported by and suspended between parts of said lower conducting region.