NOVELTY - A semiconductor device (1), comprises: a substrate (2); and a semiconductor element (3); where a porous structure layer (4) formed by silicone resin is provided between the substrate and the semiconductor layer.    USE - The semiconductor device is used in a thin film transistor circuit, a solar battery, and an image display device (claimed).    ADVANTAGE - The semiconductor device has favorable and improved properties.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are:    (1) a method for producing the semiconductor device (1), comprising: providing the porous structure layer (4) formed by silicone resin on the substrate (2); providing a semiconductor element layer (3) on the porous structure layer (4); and intermittently heating the device only from the side of the semiconductor element layer (3);    (2) a method for producing a substrate for a semiconductor element, comprising: coating a substrate (22) with a coating solution containing at least one type of alkoxysilane selected from monoalkoxysilane, dialkoxysilane, and trialkoxysilane, and tetraalkoxysilane, to form a coating film; and forming a porous layer (24) having a density of 0.7 g/cm3 or less by heating that causes hydrolysis and condensation of the alkoxysilanes within the coating film;    (3) a substrate (31) for a semiconductor element, comprising: a resin substrate (32); an adhesion layer (33) formed by a compound obtained by hydrolyzing and condensing an alkoxysilane provided on the substrate (32); and a porous layer (34) having a density of 0.7 g/cm3 or less, formed by a compound obtained by hydrolyzing and condensing an alkoxysilane, provided on the adhesion layer (33);    (4) a thin film transistor circuit, comprising: a substrate (31) for semiconductor elements; and a semiconductor element (35);    (5) a solar battery, comprising: a substrate (31) for semiconductor elements; and a semiconductor element (35); and    (6) an image display device, comprising: a substrate (31) for semiconductor elements; and a semiconductor element (35).    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic sectional view of a semiconductor device.    Semiconductor device (1)    Substrate (2)    Semiconductor element (3)    Porous structure layer (4)