My name is Akira Takeda, General Manager of the Finance and Accounting Office and Manager of the Finance Department. Today I would like to report on Ferrotec Holdings' results for the fiscal year ended March 31st, 2021. We registered JPY 91.31 billion in consolidated net sales, a YoY increase of 11.9%. Operating income stood at JPY 9.64 billion, a YoY increase of 60.3%. Net income attributable to owners of parent saw a tailwind from gain on change in equity as a result of business reorganization at three semiconductor wafer subsidiaries. This translated into a YoY increase of 363.9% to JPY 8.28 billion. In balance sheet terms, these three semiconductor wafer companies remained consolidated subsidiaries through to the end of the third quarter. Starting in the fourth quarter, these became equity method affiliates. I would now like to discuss sales and operating income by segment.
Net sales in the semiconductor equipment related business grew by 14.7% YoY. Net sales in the electronic device business grew by 28.1% YoY. Operating income in the semiconductor equipment related business grew by 47.5% YoY and by 60.8% in the electronic device business. This represents a significant increase in operating income. I would now like to give you a detailed overview of each segment, starting with the semiconductor equipment related business. The transition of our semiconductor wafer subsidiaries to equity method affiliates weighed down on sales. On the other hand, market conditions have been favorable, with strong demand for semiconductors. Sales of semiconductor materials grew by 27% YoY, while the process tool parts cleaning business too registered a significant YoY sales increase of 35%.
In the electronic device business, sales increased by 32% YoY on an increase in sales of thermoelectric modules for use in telecommunications equipment related to 5G and in medical equipment like PCR testing equipment. In terms of power semiconductor substrates, expanded production capacity for DCB substrates and the mass production of AMB substrates for automotive applications made a positive contribution. This translated into a YoY sales increase of 23%. Next, I would like to discuss the consolidated balance sheet. Our semiconductor wafer subsidiaries became non-consolidated entities, resulting in significant changes to the balance sheet. First, tangible fixed assets decreased by JPY 57.8 billion YoY. On the other hand, while these had previously been accounted for under intercompany elimination, we now include the amounts associated with accounts receivable from and loans to the semiconductor wafer equity method affiliates.
This is the result of the removal of these subsidiaries from the scope of consolidation. With that being said, we expect this amount to decrease over time as progress is made in the collection of accounts receivable and the repayment of loans. On the liabilities side, we succeeded in greatly reducing interest-bearing debt, which decreased by JPY 30.8 billion. In addition to the repayments of loans through the sale of a portion of the shares of the three semiconductor wafer companies, this decrease also resulted from the fact that bank loans associated with these three companies are now excluded from the scope of consolidation.
We were able to greatly enhance the line item of net assets, which increased by JPY 28.1 billion YoY. The restructuring of the three semiconductor wafer companies allowed us to book a gain on change in equity of JPY 5.2 billion. This translated into an increase in retained earnings. Additionally, we also registered an increase of JPY 6.2 billion in capital surplus. Furthermore, our Chinese subsidiaries carried out a capital increase through third party allotment. This translated into an increase in non-controlling interests of JPY 9.4 billion, which stood at JPY 11.1 billion.
Next are the business forecasts for the fiscal year ending March 2022. We forecast JPY 105 billion in net sales, JPY 15 billion in operating income, and JPY 7.8 billion in net income attributable to owners of parents. The deconsolidation of the three semiconductor wafer companies will be reflected throughout the entire fiscal year, leading to a decrease in sales accompanied by an increase in profit. I would now like to discuss the forecasts for each segment, starting with the semiconductor equipment related business. We expect continued growth in semiconductor-related demand.
We have registered further growth in demand for semiconductor materials, in particular, and have increased production capacity at our quartz plants in Changsha and Dongtai at the request of our customers. The start of operations at these two plants is expected to make a positive sales contribution. Additionally, we are also forecasting a sales increase for vacuum feedthroughs and in the process tool parts cleaning business. In the electronic device business, we forecast a continued increase in sales of thermoelectric modules. Regarding power semiconductor substrates, in addition to further increasing production capacity for DCB substrates, we expect further growth through the mass production of AMB substrates for automotive use. Next, I would like to discuss our fundraising activities.
The main items for the fiscal year ended March 2021 were the partial sale of shares in our semiconductor wafer subsidiaries, the repayment of JPY 40.4 billion in interest-bearing debt, and the capital increase through third party allotment carried out by our Chinese subsidiaries. Ferrotec's equity ratio recovered to 37.9%, while the ratio of net assets to total assets excluding non-controlling interests rose to 44.1%. The ratio of interest-bearing debt to net assets decreased from 1.56 to 0.61.
We were therefore able to realize a significant improvement in terms of the company's financial soundness. Here is an outline of fundraising activities planned for the current fiscal year. We are planning to carry out JPY 40 billion in investment in the current fiscal year. Of this approximately JPY 24 billion will go towards further production capacity increases in the semiconductor equipment related and electronic device businesses, which we expect will continue seeing demand growth.
The remaining JPY 16 billion will go towards strategic investments in reclaimed wafers. This therefore represents a proactive investment plan towards business and profit growth. In terms of financing, we had already raised approximately JPY 18.6 billion through third-party allotment by subsidiaries. In addition to the growth of the market for semiconductors, we are also expecting growth in the market for electronic devices, especially for use in automobiles.
Additionally, we were able to improve financial stability through the restructuring of our semiconductor wafer subsidiaries. As President He will be discussing later on in today's presentation in his discussion of the mid-term management plan, we intend on thoroughly pursuing business and profit growth and continue proactive investment. Furthermore, we have adopted a new financial structure whereby we will be incorporating into the consolidated financial statements subsidiaries that have introduced external capital from China, either as consolidated subsidiaries or as equity method affiliates.
In terms of our financial response, we will be carrying out proactive investment and position net income as a KPI. Additionally, by strengthening and making widespread the management of investment returns and ROIC, we intend to promote business operations placing emphasis on profit growth. At the same time, we would like to consider the introduction of Chinese capital, but strive to secure an appropriate balance between business, investment opportunities, and finances. We will be dedicating our efforts towards achieving further growth for Ferrotec and further increasing our corporate value.
Greetings everyone. My name is He Xian Han, Representative Director, President, and Group CEO of Ferrotec Holdings. Thank you for taking the time off your busy schedules to view today's financial results briefing. Allow me to give you a review of Ferrotec Holdings' activities in the fiscal year ended March 31st, 2021, and discuss our corporate policy and strategy over the medium to long term. We posted a record performance in the fiscal year ended March 31st, 2021.
As announced on May 14th, we registered JPY 91.3 billion in net sales, JPY 9.64 billion in operating income, and JPY 8.28 billion in net income. As you are aware, COVID-19 became a global pandemic last year, wreaking havoc the world over in 2020. As you are aware, we divide our operations into three business segments at Ferrotec. First is the semiconductor equipment related business. The second business segment is the electronic device business. Lastly, the third business segment is applications for electric vehicles.
All three business segments represent high-growth areas on a global scale. As such, in 2020 and with the support of our stakeholder base, Ferrotec was able to lay a robust foundation across a multitude of areas and build up capacity with an eye towards the future. We were also able to increase the number of production bases. Against this backdrop, we didn't focus exclusively on standalone performance for the fiscal year ended March 2021. As such, we continuously strived to find ways to further grow Ferrotec as a company. This is always at the forefront of our thought process. As you are aware, within the semiconductor equipment-related business, we deal with advanced materials. Second, we also offer services such as process tool parts cleaning, and reclaimed wafers. Third, we deal with metal precision machining and equipment parts.
As you are aware, regarding semiconductor advanced materials, the products we offer, namely quartz and ceramic products, silicon parts products, and CVD -SiC have all been showing high levels of growth. Naturally, the large diameter wafer programs are now treated on a non-consolidated basis. With that being said, our eight-inch and 12-inch wafer programs have shown rapid growth over the past year. Second are the services we offer starting with the process tool parts cleaning business. This business has already achieved a significant scale. Last year, we enacted reforms to the capital structure with an eye towards a public listing. The second service we offer is reclaimed wafers. Construction of our reclaimed wafer plant was completed last year, and we started trial operations earlier this year. We are currently in the process of fully installing the necessary equipment towards opening up for business in June of 2021.
Third, we have metal precision machining and equipment parts. Both our metal precision machining and vacuum feedthroughs registered significant growth last fiscal year. Within this, we registered significant growth associated with vacuum chambers for OEMs and with parts for use in robotics. Additionally, we have been making steady progress towards the manufacturing of semiconductor devices. Second is the electronic device business. Within this business, as you are aware, our thermoelectric modules have significant applications for 5G communication devices as well as for self-driving systems. Moreover, we further expect applications for these in the domain of telecommunications and in other industrial fields in which further growth is expected. In particular, we would like to make further use of big data going forward.
Last year, we acquired RMT Ltd., a Russian company, as a subsidiary, and we would like to further enhance our efforts to offer products for use in the domain of telecommunications. Second, we have power semiconductor substrates. Our lineup already included power semiconductor DCB and AMB substrates, and we added DPC substrates starting January of 2021. Going forward, power semiconductor substrates are expected to have applications in a wide range of areas, such as in IGBT, MOSFET, electric vehicles, high speed rail, mass rapid transit, power generation, etc . Recently, there has been a worldwide trend of companies committing to achieving towards zero CO₂ emissions by the year 2050. Against the backdrop of this trend towards zero CO₂ emissions, we believe our power semiconductor substrates business will be able to grow further.
Regarding this business, last year we announced our plan to list in the Chinese market our subsidiary in Dongtai in Jiangsu Province. Naturally, we have enacted structural reform to the capital structure. Third, we will be further dedicating our efforts to and further enhancing applications in the domain of electric vehicles. We aim to build a JPY 30 billion business over the next three years. We have held extensive discussions regarding Ferrotec's plans over the medium to long term. The company is looking to achieve the following four objectives over the medium to long term. First, we are aiming to realize sustainable business growth, namely an annual growth rate of approximately 20% over the long-term horizon. Second, we will be further fortifying our financial standing. We are currently aiming for an equity ratio of over 40% by the end of the fiscal year ending March 2024.
Third, we believe quality to be a vital component at Ferrotec. Consequently, we will seek to enhance quality control and manufacture even better products to be sold on a global scale. We have positioned two months every year as being dedicated to quality control and improvement, and we intend to continue this initiative going forward. Additionally, we are also aiming for zero customer complaints. Fourth, we will be strengthening our personnel, as personnel is the foundation allowing every business and every company to grow. As such, we believe that by strengthening our personnel, we can grow our business and develop new products. We will be taking a swift and proactive approach towards hiring talent in the form of human resources possessing doctorate and master's degrees, as well as human resources with four-year university bachelor's degrees. Going forward, we would like to dedicate our efforts to R&D.
For the fiscal year ending March 2024, we are aiming for JPY 150 billion in net sales, 16.7% in operating income margin, and a net income margin of 10%. The planned investment amount between the fiscal years ending March 2022 and March 2024 is JPY 95 billion. Of this, we will be investing JPY 55 billion in existing businesses and approximately JPY 40 billion in new businesses. We would like to carry out our operations always with an eye towards the future. As such, and as you are aware, we will be doing our utmost to deliver JPY 105 billion in consolidated net sales for the fiscal year ending March 2022. Additionally, we also want to raise the operating income margin to between 13% and 15%. In light of this, I would like to request the continued support of all stakeholders during this period of growth for Ferrotec.
We would like to execute our medium to long-term vision along the lines of the net sales and net income targets I mentioned earlier. We are strongly committed to becoming a company capable of delivering JPY 300 billion in net sales by fiscal year 2030, with a bottom-line net income performance of JPY 30 billion. By then, we believe we will have been able to further enhance the products we offer in advanced materials and devices and equipment related. We ask you for your continued support.