A humidity sensor comprising: a substrate; a reference field effect transistor; and a sensing field effect transistor; and wherein: the reference field effect transistor comprises: a source formed on the substrate; a drain formed on the substrate; a gate; a lower gate dielectric layer which covers at least a portion of the source and at least a portion of the drain as well as the substrate therebetween; and an upper gate dielectric layer of a hydrophobic polymer that overlies the lower gate insulator layer; and wherein: the layer of hydrophobic polymer of the reference field effect transistor is covered by a layer impermeable to water vapor; and the gate comprises the layer impermeable to water vapor; and the sensing field effect transistor further comprises: a source formed on the substrate; a drain formed on the substrate; a gate; a lower gate insulator layer which covers at least a portion of the source and at least a portion of the drain as well as the substrate therebetween; and an upper gate dielectric layer of a hydrophobic polymer that overlies the lower gate insulator layer; and wherein: the layer of hydrophobic polymer of the sensing field effect transistor is covered by a layer permeable to water vapor; and the gate comprises the layer permeable to water vapor. a substrate; a reference field effect transistor; and a sensing field effect transistor; and wherein: the reference field effect transistor comprises: a source formed on the substrate; a drain formed on the substrate; a gate; a lower gate dielectric layer which covers at least a portion of the source and at least a portion of the drain as well as the substrate therebetween; and an upper gate dielectric layer of a hydrophobic polymer that overlies the lower gate insulator layer; and wherein: the layer of hydrophobic polymer of the reference field effect transistor is covered by a layer impermeable to water vapor; and the gate comprises the layer impermeable to water vapor; and the sensing field effect transistor further comprises: a source formed on the substrate; a drain formed on the substrate; a gate; a lower gate insulator layer which covers at least a portion of the source and at least a portion of the drain as well as the substrate therebetween; and an upper gate dielectric layer of a hydrophobic polymer that overlies the lower gate insulator layer; and wherein: the layer of hydrophobic polymer of the sensing field effect transistor is covered by a layer permeable to water vapor; and the gate comprises the layer permeable to water vapor. the reference field effect transistor comprises: a source formed on the substrate; a drain formed on the substrate; a gate; a lower gate dielectric layer which covers at least a portion of the source and at least a portion of the drain as well as the substrate therebetween; and an upper gate dielectric layer of a hydrophobic polymer that overlies the lower gate insulator layer; and wherein: the layer of hydrophobic polymer of the reference field effect transistor is covered by a layer impermeable to water vapor; and the gate comprises the layer impermeable to water vapor; and a source formed on the substrate; a drain formed on the substrate; a gate; a lower gate dielectric layer which covers at least a portion of the source and at least a portion of the drain as well as the substrate therebetween; and an upper gate dielectric layer of a hydrophobic polymer that overlies the lower gate insulator layer; and wherein: the layer of hydrophobic polymer of the reference field effect transistor is covered by a layer impermeable to water vapor; and the gate comprises the layer impermeable to water vapor; and the layer of hydrophobic polymer of the reference field effect transistor is covered by a layer impermeable to water vapor; and the gate comprises the layer impermeable to water vapor; and the sensing field effect transistor further comprises: a source formed on the substrate; a drain formed on the substrate; a gate; a lower gate insulator layer which covers at least a portion of the source and at least a portion of the drain as well as the substrate therebetween; and an upper gate dielectric layer of a hydrophobic polymer that overlies the lower gate insulator layer; and wherein: the layer of hydrophobic polymer of the sensing field effect transistor is covered by a layer permeable to water vapor; and the gate comprises the layer permeable to water vapor. a source formed on the substrate; a drain formed on the substrate; a gate; a lower gate insulator layer which covers at least a portion of the source and at least a portion of the drain as well as the substrate therebetween; and an upper gate dielectric layer of a hydrophobic polymer that overlies the lower gate insulator layer; and wherein: the layer of hydrophobic polymer of the sensing field effect transistor is covered by a layer permeable to water vapor; and the gate comprises the layer permeable to water vapor. the layer of hydrophobic polymer of the sensing field effect transistor is covered by a layer permeable to water vapor; and the gate comprises the layer permeable to water vapor.