Methods of sealing a semiconductor element are provided. The methods includes the steps of coating a semiconductor element mounted on a gold-plated printed circuit board with a curable silicone resin, and then curing the curable silicone resin. In a method, the gold-plated printed circuit board is subjected to preliminary treatment with a treatment agent including an acid anhydride group-containing alkoxysilane and/or a partial hydrolysis-condensation product thereof In another method, the curable silicone resin includes the treatment agent. The methods yield favorable adhesion upon sealing.